Donovan made headlines last month when a grand jury he convened did not indict Officer Daniel Pantaleo for the death of Eric Garner. He is now opposing the release of details from the investigation.
Donovan, who's served as district attorney since 2003, already received widespread support from Republicans on and off the island.
He's seeking the endorsement of the Republican party to be the candidate for a special election to take over the seat, left vacant after Grimm pleaded guilty to tax evasion.
"In the week since my last announcement the enthusiasm for my candidacy has only broadened and intensified, with expressions of support also from beyond the two boroughs," Donovan said in a statement.
"Accordingly, please consider this my formal announcement that I will be seeking the endorsements of the Republican, Conservative, and Independence Parties in the upcoming Special Election for the 11th Congressional District of New York."
Assemblywoman Nicole Malliotakis also said she's seeking the nomination from the same parties, and said she hopes the Staten Island GOP takes into consideration their "rank and file members" before they make a decision on the nominee.
"It's stacked against me, because most of the members are staff members of elected officials who have already made their endorsements," Malliotakis said, who received support from the Brooklyn party and former governor George Pataki. "It's important to get the rank and file members informed... I think it's important that they're included."
Since Grimm resigned from Congress on Jan. 5, Gov. Andrew Cuomo has to set a special election to fill the spot, which hasn't been set yet. There are no primaries for special election, and candidates are appointed by the parties for the spot.
Assemblyman Michael Cusick, Councilman Vincent Gentile and Michael McMahon — who lost the seat to Grimm in 2011 — have been linked to run on the Democratic side.