Jagr, injured twice during New York's first-round playoff loss to New Jersey in the spring, hopped off the bench within the opening two minutes as the Rangers and rival Islanders were skating 4-on-4.
The sparse crowd, which included large pockets of fans supporting each team, cheered, groaned and grew more vocal when Jagr touched the puck for the first time deep in his own zone.
Jagr, the NHL MVP runner-up last season, skated in the offensive end on the same shift - carrying the puck from the left-wing boards toward the centre of the ice - before the puck was knocked off his stick by Islanders defenceman Radek Martinek 1:40 into the game.
Later in the period, Jagr skated with regular linemates Brendan Shanahan and Michael Nylander and drew a hooking penalty on Miroslav Satan when the Islanders forward held him up high in the offensive zone.
The right winger sat out the first five pre-season games, but planned to play back-to-back days as the Rangers conclude the exhibition schedule at Boston on Saturday.
In the scoreless first period, Jagr took six shifts that totalled 6:15 of ice time - 1:43 on the power play. He didn't record a shot on goal and absorbed minimal contact. Jagr was on the ice during a Rangers man-advantage when the horn sounded to end the frame.
Jagr, who set Rangers records last season with 54 goals and 123 points, was cleared earlier this week to take part in full-contact practices.
At the start of training camp, Rangers coach Tom Renney said it was doubtful Jagr would play in any exhibition games, but a positive medical report Monday changed the plan.
The 34-year-old All-Star injured his shoulder in the playoff-opening loss to the Devils. He missed one game and then returned for Game 3, but was largely ineffective after finishing second in the NHL in goals and points.
Less than one minute into the final game of New Jersey's sweep, Jagr was felled by a check from defenceman Brad Lukowich and was knocked out for good.
He had surgery nine days later on May 8.