Isaiah Jones put the hosts ahead in the 10th minute when he converted Chuba Akpom’s low cross.
Boro could have doubled their lead in the first half but were pegged back after the break when John Swift converted from Jed Wallace’s cutback.
The Teessiders will now prepare for next weekend’s trip to QPR.
Here’s how each Boro player fared at the Riverside Stadium against West Brom:
. Zack Steffen - 7
Had a few unconvincing moments early on but made two important interventions in the second half when the game was level. Left exposed for the goal. 7 Photo: Hector Vivas
. Anfernee Dijksteel - 7
Assured at the back as he dealt with the threat of Matt Phillips. Swept up danger and looked to get his side on the front foot. 7 Photo: Getty Images
. Darragh Lenihan - 7
Strong in the air against West brom striker Karlan Grant. Organised Boro’s defence and was progressive with his passing. 7 Photo: Alex Livesey
13. Marcus Forss - 6
(for Watmore, 63) Put himself about and had a couple of efforts which were blocked. 6 Photo: Alex Burstow