We measure and analyse the clustering of the Baryon Oscillation Spectroscopic Survey (BOSS) relative to the line-of-sight (LOS), for LOWZ and CMASS galaxy samples drawn from the final Data Release 12 (DR12). The LOWZ sample contains 361 762 galaxies with an effective redshift of z lowz = 0.32, and the CMASS sample 777 202 galaxies with an effective redshift of z cmass = 0.57. From the power spectrum monopole and quadrupole moments around the LOS, we measure the growth of structure parameter f times the amplitude of dark matter density fluctuations σ 8 by modeling the Redshift-Space Distortion signal. When the geometrical Alcock-Paczynski effect is also constrained from the same data, we find joint constraints on f σ 8 , the product of the Hubble constant and the comoving sound horizon at the baryon drag epoch H(z)r s (z d ), and the angular distance parameter divided by the sound horizon D A (z)/r s (z d ). We find f (z lowz )σ 8 (z lowz ) = 0.394 ± 0.062, D A (z lowz )/r s (z d ) = 6.35 ± 0.19, H(z lowz )r s (z d ) = (11.41 ± 0.56) 10 3 kms −1 for the LOWZ sample, and f (z cmass )σ 8 (z cmass ) = 0.444 ± 0.038, D A (z cmass )/r s (z d ) = 9.42 ± 0.15, H(z cmass )r s (z d ) = (13.92 ± 0.44) 10 3 kms −1 for the CMASS sample. We find general agreement with previous BOSS DR11 measurements. Assuming the Hubble parameter and angular distance parameter are fixed at fiducial ΛCDM values, we find f (z lowz )σ 8 (z lowz ) = 0.485 ± 0.044 and f (z cmass )σ 8 (z cmass ) = 0.436 ± 0.022 for the LOWZ and CMASS samples, respectively.