Studies highlight the hypocotyl diameter (HD) as an effective indicator of plant architecture (PA). Here, we estimated the genetic gain based on HD to improve PA. Twenty populations of cycles zero (C 0 ) and one (C 1 ), both in the F 4 generation, were evaluated for PA, grain yield (GY) and HD. Plants with thickest HD in C 0 were intercrossed in a circulant diallel mating design. In cycle C 1 , an estimated genetic gain of 4.93% was achieved for PA and 4.95% for HD. The populations with the highest probability of breeding lines with a thicker HD belong to cycle C 1 , and this selection strategy did not alter the GY of the populations of this cycle. Thus, indirect selection based on HD is promising for breeding for common bean PA by recurrent mass selection.