We have studied the magnetic, magnetocaloric, and magnetoelastic properties of LaFe11.57Si1.43Bx compounds in the concentration interval 0<x ≤ 1.64 using magnetization and strain gauge techniques. The crystal cell parameters and Curie temperatures were found to increase linearly with increasing B concentrations up to ∼ 0.1% and 9%, respectively. A positive magnetovolume anomaly of about 0.22% was observed in the vicinity of TC. The magnetovolume coupling constant was estimated to be approximately 3×10−3 [μB/Fe atom]−2. Magnetic entropy changes at TC slightly depended on B concentration. A hysteresis loss of about ten times smaller relative to the base compound (x = 0) was observed for x = 1.64. Therefore it was shown that the characteristics of the magnetocaloric effect of LaFe11.57Si1.43 can be adjusted by a change in B concentration in the LaFe11.57Si1.43Bx system. The relative importance of the variation in the volume of crystal cell and electron concentration on TC was discussed.