Police said it happened in broad daylight just before 7:30 a.m. on Central Park West near 70th Street.
Surveillance cameras captured the attack on the 67-year-old "Honey I Shrunk the Kids" and "Ghostbusters" actor.
Video shows the suspect, ironically wearing an "I Love New York" sweatshirt, walk up and punch Moranis in the head, knocking him to the ground.
Police said Moranis went to the hospital with pain in his head, back and hip. He later walked to the precinct to report the crime.
The NYPD's new community affairs rapid response team checked on Moranis, as it does with many victims of violent crimes to offer support, groceries, or anything they may need.
"He's doing well. He's strong. He's recovering. He has some injuries to his left side," Det. Kaz Daughtry told CBS2's Jenna DeAngelis.
"He just wants to stay home. He just wants to recover and he just wants peace of mind," said Officer Jonadel Dorrejo.
Meantime, the search continues for the suspect. Police are asking the public to be on the lookout.
Moranis' management team told CBS2 he is "fine, but grateful for everyone's thoughts and well wishes."
Neighbors said he's a very nice guy, and they were shocked to hear about the unprovoked attack.
"That why we moved here - to be safe," said resident Jonathan Kurtin. "Everything's been good, but I guess trying times. People do strange things, and they're not always nice... You'll be looking over your shoulder a lot more often."
"I'm worried about the whole situation. I'm worried about the fact that everybody's troubled and they're so troubled there's more crime," a woman who lives in the same building as Moranis said.
She also left him a note.
"I said I was really sorry to hear about it. It must've been scary," she said. "We were on the board together of this building. Nice guy. Really nice guy."
Moranis has been off the big screen for years to focus on his children after his wife's passing, but recently appeared in a Mint Mobile commercial with Ryan Reynolds.
Reynolds tweeted Friday:
Anyone with information about the attack is asked to call the NYPD's Crime Stoppers hotline at 1-800-577-TIPS (8477), or for Spanish, 1-888-57-PISTA (74782). You can also submit a tip via their website or on Twitter, @NYPDTips. All calls are kept confidential.
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