He goes into the squad for Saturday's away game against Bradford, the club where the 28-year-old has been on loan at for the last three months.
Farrelly hasn't featured in the Bolton first team this season and spent two months on loan at Burnley earlier in the campaign.
He then went to Bradford, making 15 appearances, the last of those being just 10 days ago.
With the Bantams in administration, they couldn't keep him on, and the former Republic of Ireland international returned to the Reebok Stadium.
Bolton have now come to an agreement to settle up the remainder of his contract, leaving Farrelly free to find new employers.
It is believed Walsall also offered him terms, but he has chosen to aid Latics' push towards the Premiership.
Farrelly can play in centre midfield and on the left wing.
And with Alan Mahon missing training yesterday due to a tight hamstring, he could go straight into the side at Valley Parade.
Jewell stated last week that he was looking to add two signings before the transfer deadline later this month.
And with one on board, he may now look to strengthen the cover at the back for the final run-in.
Farrelly started his career in Ireland with Home Farm before signing for Aston Villa in 1992.
He had a two-year stint at Everton before joining Bolton after a spell on loan in 1999.
Meanwhile, defender Matt Jackson is mulling over the offer of a new one-year contract.
The stand-in skipper is eager to stay at Latics and will make his decision later in the season.
Jackson was made the offer soon after QPR showed an interest in taking him to Loftus Road in January.
He said: "The manager has basically promised me another year for next season if I want it.
"I have told him I need to be playing at this stage of my career or at least be close to getting into the team which is how it is at the moment.
"But I don't want to get away, I'm settled with my family here and there are other things going on in the area as well. I'm happy to stay and hopefully will sign again for next season.
"I've known about the offer for about six weeks now, when the QPR situation came up. It would have been easy for the manager to say the offer didn't come in, but he was perfectly honest and gave me the choice.
"He asked me how I was feeling, we had a fair exchange of views, shook hands and that was it.
"It was a word of mouth offer but there will be a contract of some sort."
Jackson is one of a number of Latics players who are looking for new deals this summer.
Andy Liddell, Jason de Vos, Paul Mitchell, Gary Walsh and Mike Flynn are the others.
Jewell has previously gone on record to say he would like to offer them all a deal to reward their loyalty.
Source: Wigan Evening Post.