His bloc won more than 70% of the vote, the country's election commission said.
A journalist turned politician, Mr Pashinyan spearheaded a peaceful revolution in April.
He now has a parliamentary majority to push through his programme of tackling corruption and reforming the economy. Poll turnout was low, at about 49%.
Historically, Armenia's elections have been marred by fraud and vote-buying.
However, international observers from the Organization for Security and Co-operation in Europe said the elections had respected fundamental freedoms and were characterised by genuine competition.
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