He was reportedly paid a salary of around £1,000 per week at the Royals, a fraction of the wage he would've received at any of the Premier League outfits he signed for.
The decision to join Veljko Paunovic's ranks was thought to be fuelled by a love of the game, and to get his career back on track.
He was signed in time to feature against Millwall on Saturday, with the striker likely to start on the bench.
He could provide Valerien Ismael with a much-needed differential option in attack.
What can Carroll bring to the table?
Making a total of eight appearances during a two-month spell at the 'Ding, the 33-year-old provided a goalscoring touch, bagging two goals.
As expected, the Gateshead-born forward proved to be a handful, providing an aerial threat and bullying centre-forwards.
He scored his first goal less than two weeks after signing for the club in a 3-2 win against Swansea City, controlling a high ball over the top and twisting past two defenders to drive a low shot past the goalkeeper.
His second came in his final game for the club, a typical looping header saw the Royals grab the opening goal in their eventual 2-1 defeat to Middlesbrough.
Although naturally, questions will be raised over his fitness levels, however, having last played EFL Championship football only two weeks ago, Carroll's match fitness means he could slot straight in.
His ability to win aerial duels and hold the ball up will be extremely useful for Ismael, with on-loan Norwich City forward Jordan Hugill and outcast Kenneth Zohore nowhere to be seen in recent matchday squads.
Speaking to WBA.co.uk Ismael said:
“Andy is a player who is able to help us straight away. He is ready and brings with him all the attributes we need. It could be a win-win situation for us.
“The fact Andy has played plenty of games for Reading recently is great. He’s fit after playing those games and he’s scored goals during that short-term deal. Hopefully, Andy can now score goals for us.
“After the Dike injury, we assessed the situation, because it is a big loss, and it was clear that he had made an impact in that short time. We needed to replace him, and we are pleased to welcome Andy who has a lot of experience.”
New striker Dike will miss roughly eight weeks of action after picking up a hamstring injury in their win over Peterborough United.
The American signed for around £7 million on the opening day of the January transfer window from Orlando City.
After signing on a four-and-a-half-year deal, the forward was deemed to be the final piece in the puzzle for boss Ismael.
However, in his absence, they've added another target man into the Baggies ranks in Carroll.