He replaced German conservative Hans-Gert Poettering as parliament president. In the vote, Eva-Britt Svensson MEP, a Swedish leftist, came second with 89 votes.
Mr Buzek will hold the post for two-and-a-half years - half of the parliament's five-year mandate. Under a deal struck before Tuesday's vote, a Socialist MEP will serve as president for the other half.
"We have to realise that we're in a crisis now. Europeans are expecting a resolution of this problem," he said.
He called his election "a tribute to the millions of people who didn't bow to a hostile system" - a reference to the democratisation of the former Soviet bloc.
"There is now no 'you' and 'us' - we live in a shared Europe," he stressed.
MEPs will postpone for at least two months a vote on reappointing European Commission chief Jose Manuel Barroso, a veteran Portuguese conservative.
The new parliament includes far-right groups that made gains in June, including the British National Party.
It is not clear how British MEPs from the political mainstream will interact with their two colleagues from the BNP.
The BNP has failed to form a new bloc with other far-right MEPs, who include politicians from Hungary's Jobbik, France's National Front, Belgium's Vlaams Belang, Bulgaria's Ataka, the Danish People's Party and the Dutch Freedom Party.
June's election produced a clear victory for centre-right parties across Europe.
Although the 25 British Conservative Party MEPs have left the European People's Party to form the European Conservatives and Reformists Group (ECR), the EPP remains the strongest bloc in parliament with 264 seats.
The centre-left Progressive Alliance of Socialists and Democrats in Europe (PASDE) is the second largest bloc with 183 MEPs, followed by the Alliance of Liberals and Democrats for Europe (ALDE) with 84.
Quite how influential the ECR will be in the new parliament should become clear when the members and chairmen of the powerful committees are decided, says the BBC's Dominic Hughes in Strasbourg.
The president sets the tone of the parliament and can rule on points of order, our correspondent says. The post holder also represents the assembly to heads of state and government.
Absent from the session, however, will be a vote on the reappointment of Mr Barroso as president of the European Commission, the EU's executive arm.
The former Portuguese PM has the support of all 27 member states, but his centre-right allies in the assembly do not have a majority.
The Swedish presidency, which took over from the Czech Republic on 1 July, will lay out its priorities for the next six months on Wednesday.
EPP - European People's Party (Christian Democrats)
S&D - Progressive Alliance of Socialists and Democrats in Europe (centre-left)
ALDE - Alliance of Liberals and Democrats for Europe (liberal)
GUE/NGL - European United Left-Nordic Green Left (left-wing)
Greens/EFA - Greens/European Free Alliance (Greens and regionalists/nationalists)
ECR - European Conservatives and Reformists Group (right-wing)
EFD - Europe of Freedom and Democracy (Eurosceptic)
NA - Non-attached (MEPs not part of any group)
The number of MEPs will increase to 754 if the Lisbon Treaty comes into force.
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