Smith was activated off the non-football injury list Thursday. He went into an alcohol treatment center Sept. 23 -- three days after his second arrest on suspicion of drunken driving since entering the NFL in 2011. He was released from the treatment center this week.
Smith met with coach Jim Harbaugh on Wednesday.
"I met with him face to face today," Harbaugh told San Francisco radio station 95.7 The Game on Wednesday. "Aldon was in the building. ... It was great to see the reaction of others who saw him and Aldon's reaction of being back here with some of the guys. He looks great, and we're having a good day. I mean, that was the object of today -- let's have a great day. I think that's the way Aldon's approaching things each day too ... the goal to have a great day."
San Francisco general manager Trent Baalke said last week he is hopeful Smith will play this season but that the team wants to see "progress" from its young linebacker. Sources said Thursday the team believes Smith is ready to get back to the daily life of being an NFL player and that it is best for him to be with the team.
Smith, 24, is expected to play in the 49ers' next game, Nov. 10 at home against Carolina. Smith has 4.5 sacks in three games this season and has an NFL-leading 38 sacks since 2011.
The 49ers will have a roster exemption for a week for Smith. Therefore, he can practice for a week and the team won't have to make a roster move until the day before the Carolina game.
On Saturday, in London, NFL commissioner Roger Goodell said the fact that Smith sought treatment and missed five games on his own will be factored in when the league determines if he will be suspended. The league could opt to fine Smith and take away a game check or two.
Out of good faith, the 49ers paid Smith while he was gone. His game check was about $99,000 a week.
Smith was charged Oct. 9 with three felony counts of illegal possession of an assault weapon, stemming from a party at his home in June 2012. Smith will be due in court twice -- Nov. 12 and Nov. 19 -- to face DUI and weapons charges.
Also in September, Smith and former teammate Delanie Walker were named in a lawsuit filed in Santa Clara County Superior Court by a Northern California man who said he was shot at a party at Smith's house on June 29, 2012.
The players charged a $10 admission and $5 per drink, the lawsuit said. Smith and now-Titans tight end Walker, 29, were allegedly intoxicated on Smith's balcony when they fired gunshots in the air while trying to end the party, the lawsuit said.
Before the 2012 home opener last September, Smith was the passenger in a car during an accident in Santa Clara County in which the driver swerved to avoid hitting a deer. Smith sustained a cut beneath his right eyebrow. He apologized and insisted he would change his ways.
Smith, selected seventh overall in the 2011 draft out of Missouri, had previously been arrested on suspicion of DUI in January 2012 in Miami shortly after the 49ers lost in the NFC Championship Game.
The 49ers are 5-0 since Smith left. However, his return will give the team a spark as it heads into the stretch run.
Information from The Associated Press was used in this report.