However, the party acknowledged that the result was not as "overwhelming" as it had expected and said it would examine the reason behind it.
"MCD ruled by BJP-Congress. Outsider AAP wins maximum seats in by election. Thnx Delhi for reaffirming faith. Ab MCD election mein sabhi seat jeetni hain(sic)," party chief Arvind Kejriwal tweeted.
Out of the 13 wards that went to by-polls, AAP won from Matiala, Tekhand, Nanakpura and Vikas Nagar and Ballimaran.
"AAP has emerged as the largest party in the by-polls. This means it is bigger than BJP and Congress. This was our debut and it was great learning experience.
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"We had expected a few more seats. We will examine why the result didn't match our expectations. For this, we will hold discussion with the MLAs to assess what went wrong," AAP's Delhi unit convener Dileep Pandey said.
He said the MCD by-polls were not a parameter to assess the popularity of the state government.
"BJP lost a gram panchayat election in a village adopted by Prime Minister Narendra Modi. Congress lost civic body polls in Rahul Gandhi's constituency. So there is hardly any link between popularity of any leader or a party as issues are completely different in MCD polls," Pandey said.
Terming the by-polls as a "launchpad" to the "mega final" next year, he said the results show that AAP has the capability of "restricting BJP to minimum numbers".