Since 1929, the People's Party (known until 1971 as the Party of Farmers, Traders and Independents [BGB]) had held a seat on the seven-member Swiss Federal Council. At the time the current coalition formed in 1959, the BGB was the smallest party represented on the Council. By 2003 it had become the largest party, and demanded another seat at the expense of the Christian Democrats, now the smallest party. The SVP nominated Blocher as its second candidate. This generated a good deal of controversy; previously most SVP councillors had come from the party's more moderate centrist-agrarian wing.

The son of a pastor, Blocher was born in 1940, the seventh of eleven children.

Blocher earned a certificate at the Wülflingen school of agriculture. In 1961, Blocher began studying independently for the Swiss Matura. In 1963, Blocher completed and passed the exams for the Swiss Matura and in 1964, he passed an additional exam in Latin to pursue legal studies at university. Then studied law at the University of Zürich, in Montpellier and in Paris. He has a DEA degree in law, and in 1971, he was awarded a doctorate in jurisprudence from the University of Zürich.

While at the University of Zürich, Blocher co-founded the Students' Ring, which opposed the 1968 student protests and the left-wing politics on university campuses.

Blocher started working at EMS-Chemie in 1969 as a student in its legal department. In 1972, Blocher was voted Chairman of the Board and CEO of the company, and in 1983, he purchased a majority of EMS-Chemie.

When Blocher was elected President of the Zürich SVP in 1977, he declared his intent to oversee significant change in the political line of the Zürich SVP, bringing an end to debates that aimed to open the party up to a wide array of opinions. Blocher soon consolidated his power in Zürich, and began to renew the organisational structures, activities, campaigning style and political agenda of the local branch. The young members of the party were boosted with the establishment of a cantonal Young SVP (JSVP) in 1977, as well as political training courses. The ideology of the Zürich branch was also reinforced, and the rhetoric hardened, which resulted in the best election result for the Zürich branch in fifty years in the 1979 federal election, with an increase from 11.3% to 14.5%. This was contrasted with the stable level in the other cantons, although the support also stagnated in Zürich through the 1980s.

Blocher built his political career through campaigning for smaller government, for a free-market economy, against Switzerland's membership in the European Union and for more tightly controlled immigration. He stated he entered the political arena by chance due to a local zoning dispute. Blocher joined the SVP in 1972 and became the SVP President of the SVP chapter in Meilen in 1974. After being elected to the Cantonal Council of Zürich in 1975, Blocher was elected to the Swiss National Council and represented the canton of Zürich there from 25 November 1979 until his election to the federal council on 12 December 2003 as a deputy of the Swiss People's Party (Schweizerische Volkspartei/Union démocratique du centre; SVP/UDC), and then again from 4 December 2011 to 30 May 2014.

In addition to leading the Zürich chapter of the Swiss People's Party, Blocher was a cofounder of the Action for an Independent and Neutral Switzerland (Aktion für eine unabhängige und neutrale Schweiz), and he served as the President of the organization from its foundation in 1986 until his election to the Federal Council in 2003.

The struggle that existed between the SVP's largest branches of Bern and Zürich continued into the early 1990s. While the Bern-oriented faction represented the old moderate style of the SVP, the Zürich-oriented wing led by Blocher represented a new radical right-wing populist agenda. The Zürich wing began to politicise asylum issues, and the question of European integration started to dominate Swiss political debates. They also adopted more confrontational methods. The Zürich-wing followingly started to gain ground in the party at the expense of the Bern-wing, and the party became increasingly centralised as a national party, in contrast to the traditional Swiss system of parties with loose organisational structures and weak central powers. During the 1990s, the party also doubled its number of cantonal branches (to eventually be represented in all cantons), which strengthened the power of the Zürich-wing since most new sections supported their agenda. Although Swiss political parties tended to lack dominant national Leaders, Blocher became the de facto leader of the national SVP and one of the most famous Swiss politicians.

In 1991, the party for the first time became the strongest party in Zürich, with 20.2% of the vote. The party broke through in the early 1990s in both Zürich and Switzerland as a whole, and experienced dramatically increasing results in elections. From being the smallest of the four governing parties at the start of the 1990s, the party by the end of the decade emerged as the strongest party in Switzerland. At the same time, the party expanded its electoral base towards new voter demographics. The SVP in general won its best results in cantons where the cantonal branches adopted the agenda of the Zürich wing. In the 1999 federal election, the SVP for the first time became the strongest party in Switzerland with 22.5% of the vote, a 12.6% share increase. This was the biggest increase of votes for any party in the entire history of the Swiss proportional electoral system, which was introduced in 1919.

In December 2003, the New York Times published a letter from the Anti-Defamation League citing Blocher, who had been convicted for anti-Semitic libel by a Zürich court in 1999, for making anti-Semitic remarks in relation to claims for restitution of Nazi-seized assets that were hidden in Swiss banks. Blocher declared that Jews "were only interested in money." The letter also reported that in 1997, Blocher had stated the following that had resulted in his 1999 conviction: "They (the Jews) could blackmail banks, you can blackmail governments, you can blackmail national banks, you can force them to give in. (But) I would like to see if they can blackmail an entire people at the ballot box. They have to get through the eye of this needle, and I will do my utmost that we do not yield."

During 2004, Blocher's unconventionally unaccommodating stance towards his fellow federal councillors was the cause for speculations about the Future of the Swiss concordance system. He was attacked by his colleague Pascal Couchepin in an interview with the NZZ newspaper in the Sunday edition of 3 October. This was unprecedented in Switzerland; members of the Federal Council traditionally do not publicly criticise each other.

In a public speech held at his cantonal party's annual Albisgüetlitagung in Zürich on 20 January 2006, Blocher labeled two Albanians seeking political asylum as "criminals", although no judicial verdict had been reached at the time. Later, when confronted, he claimed before the Swiss Council of States (the upper house) that he had only used the word 'accused'. Since the speech had been recorded, he then had to admit that he had used the word "criminals". In July 2006, a commission of the Council of States reprimanded Blocher, stating that the setting of false prejudice and making false statement to the Council of States constituted unacceptable behaviour for a Federal Councillor.

In the Swiss Federal Council elections of 12 December 2007, Blocher did not receive the necessary number of votes in the parliament to retain his seat. In his stead, the parliament elected Eveline Widmer-Schlumpf (a moderate SVP member), who accepted the mandate on 13 December 2007. Blocher thus became the fourth federal councillor to be ousted from office in the history of the Swiss Federal State, following Ruth Metzler whom he had replaced the previous term, besides Ulrich Ochsenbein and Jean-Jacques Challet-Venel in the 19th century.

After the extremely large 2007/2008 losses posted by UBS, its chairman Marcel Ospel resigned on 1 April 2008, and Mr. Blocher was rumoured to be considered as his replacement. However the role went to Peter Kurer, the bank’s general counsel.

In January 2012, it was reported that Blocher had received information from an unnamed whistleblower regarding foreign exchange trades at Bank Sarasin made by Swiss National Bank chairman Philipp Hildebrand's wife Kashya. The alleged whistleblower was subsequently fired and faced Criminal investigations under Swiss banking secrecy laws. Hildebrand denied accusations of insider trading, claimed to be the "victim of a smear campaign" and said that his political foes endangered the secrecy laws and "the interests of Switzerland" with the accusations. Blocher had called for Hildebrand's resignation in 2011 in the wake of SNB's foreign exchange-related losses and continued strong calls after the FX-trades story grew, before Hildebrand ultimately resigned.

Blocher announced that he would resign from the National Council on 31 May 2014, saying that he was “wasting too much time in parliament” and that he wanted to focus on other political priorities like the implementation of the successful referendum "Against mass immigration" and a planned initiative on preventing Switzerland joining the European Union.

In an interview in April 2016, Blocher stated that United States President Ronald Reagan "was the best President I have seen" and that he thought that, like Reagan, then-presidential candidate Donald Trump would be underestimated but more competent and great than expected. After Trump's election victory, Blocher stated that his victory was a warning to world Leaders not to ignore the people's concerns on issues such as immigration, saying "people feel powerless against those who rule them, and for them, Trump is a release valve."

In March 2018, the SVP announced that Blocher would resign as the party's chief strategist, though he would continue to remain involved in Swiss politics.