The figures put the likely GOP nominee's fundraising haul closer to the $43.6 million that President Barack Obama and the Democratic Party raised last month. Romney's campaign pulled in about $12.5 million in March.
April's reports offer the first fundraising tallies of the general election. Romney began raising cash with the GOP last month.
The new fundraising totals don't include the hundreds of millions of dollars being spent by "super" political committees that can raise and spend unlimited sums of cash.
Both campaigns' detailed financial reports are due to the Federal Election Commission by midnight Sunday.