We present a measurement of b jet transverse momentum (pT)spectra in proton-lead (pPb) collisions using a dataset corresponding to about 35nb⁻¹ collected with the CMS detector at the LHC. Jets from b quark fragmentation are found by exploiting the long lifetime of hadrons containing a b quark through tagging methods using distributions of the secondary vertex mass and displacement. Extracted cross sections for b jets are scaled by the effective number of nucleon–nucleon collisions and are compared to a reference obtained frompythiasimulations of pp collisions. Thepythia-based estimate of the nuclear modification factor is found to be 1.22 ±0.15 (stat+systpPb) ±0.27 (systpythia)averaged over all jets with p_T between 55 and 400GeV/cand with |η_lab|<2. We also compare this result to predictions from models using perturbative calculations in quantum chromodynamics.