- Kieffer Moore (32')
- Kevin De Bruyne (12')
Despite having already assured themselves of a place in the playoffs next March courtesy of their Nations League results, finishing second in the group means that Robert Page's side could enjoy a more favourable semi-final draw.
Belgium, who won the group with 20 points, appeared content to maintain their long unbeaten run in World Cup qualifiers which now stretches to 28 games.
Wales, who have not lost a home qualifier for four years, are trying to reach the World Cup finals for the first time since 1958 and will at least know that they cannot play either Italy or Portugal in their playoff semi-final.
"It's massive. Full credit to the boys, they put in a massive shift again against top opposition," Wales captain Aaron Ramsey said. "There's some big, big teams still in it but it was so important that we had a home tie."
Things did not start well for Wales and it took Belgium only 12 minutes to go ahead with De Bruyne clinically dispatching a right-foot shot inside the post after an effort by Axel Witsel rebounded into his path off a Welsh defender.
Belgium looked in the mood to make Wales suffer and De Bruyne wasted a chance after a mistake by Ben Davies.
But Wales unexpectedly drew level when Daniel James showed great persistence on the left to eventually play in a cross to Moore who swept a shot past Casteels.
Belgium almost went back in front before halftime when De Bruyne chipped a free kick towards Thorgan Hazard whose first-time volley smacked against the upright.
Roberto Martinez's side continued to enjoy the lion's share of possession after the break but Wales always looked dangerous on the counter and were well worth a point that could prove vital if they are to take their place in Qatar in 12 months.
Only three of the 12 teams competing in the playoffs, who will be separated into groups of four with each group featuring two single-leg semi-finals and one final, will reach the World Cup in Qatar.