The former France striker, who could begin his second spell by playing a part in Monday's FA Cup third-round match against Leeds, scored a club-record 226 goals for Arsenal in 370 appearances between 1999-2007.
He is held in such high esteem by the club's fans that he was voted the team's greatest player in a poll on its official website in 2008.
There is also a bronze statue of Henry outside the Emirates stadium but the 34-year-old striker warned supporters not to expect the same player who terrorized defences across England and in Europe in his first stint at Arsenal.
"I am not coming here to be a hero or prove anything. I am just coming here to help. People have to understand that," Henry said.
"I'll be on the bench most of the time. If I can make the bench, that is."
Henry had to wait a week to secure the temporary switch while Arsenal finalized insurance agreements with the New York Red Bulls, his club in Major League Soccer. He will return to the United States for the new MLS season, which starts on March 10.
Arsenal manager Arsene Wenger is turning to Henry to fill the gap in his strikeforce left by the departure of Gervinho and Marouane Chamakh to the African Cup of Nations.
"It is unreal to be honest. But when it comes to Arsenal, my heart will always do the talking," Henry said.
"I always said I was never going to come back and play in Europe again but when the team you love and support asks you back, it's kind of hard to say 'no,'" he added.
Henry will be available for January and most of February, meaning France's record goalscorer could feature in six league games — including the home match against Manchester United on Jan. 22.
There is a chance he could also feature in the north London derby against Tottenham on Feb. 26, although he said may choose to return to New York before then to prepare for the MLS season.
"Even if it is just five seconds, one second, or just talking in the dressing room, I will give my best whatever it is," Henry said.
Without a major trophy since 2005, Arsenal is currently fifth in the Premier League, 12 points behind leader Manchester City and one behind Chelsea — which holds the fourth and final Champions League spot.
"I am sure during these two months he will be a massive asset to the team in the dressing room and on the pitch," Wenger said. "He can be relaxed, not under too much pressure and be a tremendous help to the team."
Henry will act as one of the backups to Robin van Persie, who has taken over the Frenchman's mantle as Arsenal's star attacker and scored 17 league goals this season.
In 2011, Van Persie scored 35 times in the league, breaking the club record for a calendar year set by Henry by one goal.
"Right now Robin is flying. I can be around and talk to him but he is doing what he does best — scoring goals," Henry said. "When the boss spoke to me about coming back, I wanted to make sure I didn't disturb the team that was in place. That was important to me."
South Korea captain Park Ju-young, who has struggled for first-team chances since his move from Monaco in the off-season, is the other striker in Arsenal's squad.
The bronze statue outside Emirates stadium was one of three, along with those of former captain Tony Adams and ex-manager Herbert Chapman, made to celebrate the club's 125th-year anniversary in December.
"Here I am now a few weeks later playing for Arsenal," Henry said. "It wasn't planned."