In light of the charges, the Browns announced the release of the player they had signed on May 13 as an undrafted free agent out of Virginia.
Authorities told The Bergen Record that Walcott punched Derrick Jones in the head just after The Palace Gentlemen's Club closed early Sunday morning.
Police say Jones, who is from New York City, is in critical condition. Walcott, 23, is held on $500,000 bail. He is charged with first-degree attempted murder, second-degree aggravated assault and third-degree endangering an injured victim, said Salvatore Bellomo, a senior assistant prosecutor.
Walcott is one of 28 NFL players arrested since this year's Super Bowl on Feb. 3, according to a database kept by U-T San Diego.
In 45 games for Virginia, Walcott totaled 128 career tackles, 1.5 sacks, four passes defensed and one fumble recovery.
This isn't the first time Walcott has been arrested. In January 2011, he faced charges of assault and battery from a fight while he was at Virginia. Walcott was suspended from the team but was reinstated after charges were dropped.
Walcott is the second Browns rookie to be arrested. Seventh-round selection Armonty Bryant was charged with drunken driving in Oklahoma less than one week after the Browns picked the defensive end in April's draft. Bryant, also arrested on a felony drug charge in college, said Tuesday he has been working hard to stay clean.
Information from The Associated Press was used in this report.