Spherical harmonic coefficients of the Mars gravity field to degree 6, mass, spin‐axis direction, and the orbits of Phobos and Deimos were determined from radio and optical data obtained by the Mariner 9 spacecraft. The optical data consist of 62 TV photographs of Phobos and Deimos. The radio data are in the form of apoapsis state vectors obtained from 195 one‐revolution fits of the Doppler data. A first‐order analytical theory was used to model the motion of both the satellites and the spacecraft. However, the resonance arising from the fact that the orbital period of Mariner 9 was very close to ½ day necessitated development of a partial second‐order theory to model the long‐period perturbations by even‐order tesseral harmonics. Results for the spherical harmonic coefficients are in good agreement with those previously published from Mariner 9 Doppler data. The value obtained for the gravitational constant of Mars (42,828.1±0.5 km3/s2) is in excellent agreement with prior determinations from Mariner flyby trajectories. The direction of Mars' rotational pole relative to the earth's mean equinox and equator of 1950 is given by α = 317.3°±0.1°, δ = 52.7°±0.1°. The longitudes for Phobos and Deimos at the time of Mariner 9 Mars orbit insertion were found to be 0.2° less and 0.3° greater, respectively, than the longitudes predicted for this epoch by A. T. Sinclair (1972) on the basis of a recent processing of earth‐based data obtained for the satellites during 1877–1969.