Low P availability in the soil is a major constraint to legume production, and efforts are being made to identify legume genotypes with tolerance to low P and greater phosphorus use efficiency (PUE) for N2 fixation. Common bean (Phaseolus vulgaris L.) genotypes vary in their adaptation to low-P soils. To investigate to what extent this variation may be related to PUE for N2 fixation, six recombinant inbred lines (RILs) of common bean contrasting in PUE for symbiotic N2 fixation, namely RILs 147, 115, 104, 83, 34, and 29 were studied in the field conditions during four growing seasons from 2011 to 2015. We collected biomass (aboveground and belowground) at flowering stage, and both samples were analyzed P content. Results indicate that low-P availability in the soil significantly limited plant growth, nodulation, and N2 fixation for all common bean RILs though with highest extent for common bean RILs 147, 83, and 29, whereas in this soil, common bean RILs 34 and 104 showed highest PUE for their N2 fixation. The genotypes with high PUE for N2 fixation showed greater mycorrhizal-plant symbiosis activity rate than the genotypes with low PUE for N2 fixation. We also found a significant correlation between nodule biomass and nodule P content for all common bean RILs. We conclude that quantifying PUE for N2 fixation may contribute to characterize the level of adaptation of N2–fixing legumes to low-P soils