No, gravity is influenced very much by the mass of the object in question. This means that, in order for the gravity of Mars to be affected, we would somehow have to either add mass to the Red Planet or take it away. Terraforming Mars – that’s making it more hospitable for human habitation – does neither of these things.
Instead, terraforming Mars involves the incredible feat of building up its atmosphere, keeping the globe warm and keeping that atmosphere from being lost to outer space. Mars’s gravity (which is 38% that of Earth’s) combined with its questionable magnetic field means that, throughout its history, its atmosphere has been stripped away by the solar wind. Now, a thin layer of mostly carbon dioxide, that makes Mars quite unfriendly for humans, covers the planet. And, with no way of adding mass to the planet to increase its gravity for a much-needed atmosphere to be sustained, we would need to resort to another plan – we would have to bring gases and other materials to Mars ourselves.
Importing gases such as ammonia, hydrogen and organic materials from other celestial bodies would be the way to go as well as sublimating the ice at the Martian south pole to a gas, releasing the carbon dioxide trapped within it, which would, in turn, increase the atmospheric pressure. Plants could also be brought to the surface to create oxygen for us to breathe.