Cool M dwarfs within a few tens of parsecs from the Sun are becoming the focus of dedicated observational programs in the realm of exoplanet astrophysics . Gaia , in its all-sky survey of > 10 ^ { 9 } objects , will deliver precision astrometry for a magnitude-limited ( V = 20 ) sample of M dwarfs . We investigate some aspects of the synergy between the Gaia astrometric data on nearby M dwarfs and other ground-based and space-borne programs for planet detection and characterization . We carry out numerical simulations to gauge the Gaia potential for precision astrometry of exoplanets orbiting a sample of known dM stars within \sim 30 pc from the Sun . We express Gaia detection thresholds as a function of system parameters and in view of the latest mission profile , including the most up-to-date astrometric error model . Our major findings are as follows : ( 1 ) It will be possible to accurately determine orbits and masses for Jupiter-mass planets with orbital periods in the range 0.2 \lesssim P \lesssim 6.0 yr and with an astrometric signal-to-noise ratio \varsigma / \sigma _ { \mathrm { AL } } \gtrsim 10 . Given present-day estimates of the planet fraction f _ { p } around M dwarfs , \approx 10 ^ { 2 } giant planets could be found by Gaia around the sample . Comprehensive screening by Gaia of the reservoir of \sim 4 \times 10 ^ { 5 } M dwarfs within 100 pc could result in \sim 2600 detections and as many as \sim 500 accurate orbit determinations . The value of f _ { p } could then be determined with an accuracy of 2 % , an improvement by over an order of magnitude with respect to the most precise values available to-date ; ( 2 ) in the same period range , inclination angles corresponding to quasi-edge-on configurations will be determined with enough precision ( a few percent ) so that it will be possible to identify intermediate-separation planets which are potentially transiting within the errors . Gaia could alert us of the existence of 10 such systems . More than 250 candidates could be identified assuming solutions compatible with transit configurations within 10 % accuracy , although a large fraction of these ( \sim 85 \% ) could be false positives ; ( 3 ) for well-sampled orbits , the uncertainties on planetary ephemerides , separation \varrho and position angle \vartheta , will degrade at typical rates of \Delta \varrho < 1 mas yr ^ { -1 } and \Delta \vartheta < 2 deg yr ^ { -1 } , respectively . These are over an order of magnitude smaller than the degradation levels attained by present-day ephemerides predictions based on mas-level precision HST/FGS astrometry ; ( 4 ) planetary phases will be measured with typical uncertainties \Delta \lambda of several degrees , resulting ( under the assumption of purely scattering atmospheres ) in phase-averaged errors on the phase function \Delta \Phi ( \lambda ) \approx 0.05 , and expected uncertainties in the determination of the emergent flux of intermediate-separation ( 0.3 < a < 2.0 AU ) giant planets of \sim 20 \% . Our results help to quantify the actual relevance of the Gaia astrometric observations of the large sample of nearby M dwarfs in a synergetic effort to optimize the planning and interpretation of follow-up/characterization measurements of the discovered systems by means of transit survey programs , and upcoming and planned ground-based as well as space-borne observatories for direct imaging ( e.g. , VLT/SPHERE , E-ELT/PCS ) and simultaneous multi-wavelength spectroscopy ( e.g. , EChO , JWST ) .