The 2012/13 budget was approved with 123 votes in favor, 46 against, and 14 abstentions among the 200 members present in parliament.
The 2012/13 budget is based on an oil price of $85 per barrel, higher than last year's break even price.
The official exchange rate for the 2012/13 budget was set at 12,260 rials to the dollar.
The country is undergoing what the government has called major economic surgery, in the form of cuts to the multi-billion dollar subsidies.
Ahmadinejad has said the new budget will decrease Iran's dependency on oil revenues.
He presented the draft budget to parliament in February based on a 20 percent rise in tax revenues.