Connecting neural circuit output to behavior can be facilitated by precise chemical manipulation of specific cell populations. Local delivery of neuromodulators within the brain allows linking of their molecular targets to behavior. The engineered receptors exclusively activated by designer small molecules enabled manipulation of specific neural pathways. Their application to studies of behavior, has so far been limited by the low temporal resolution and the need for invasive implanted cannulas or infusion pumps. Here, we developed a remotely controlled chemomagnetic modulation – a technique to pharmacologically modulate targeted neural population with temporal and spatial precision in freely moving mice. The heat dissipated by magnetic nanoparticles in the presence of alternating magnetic fields triggered small molecule release from thermally sensitive lipid vesicles with 20 s latency. Coupled with chemogenetic activation of engineered receptors, this technique permitted control of the activity of specific neurons. Delivery of chemomagnetic particles to the ventral tegmental area allowed remote temporally precise modulation of motivated behavior in mice. Furthermore, the chemomagnetic approach could activate endogenous circuits by enabling regulated release of receptor ligands. Applied to a dopamine receptor D1 agonist in the nucleus accumbens, chemomagnetic modulation increased sociability in wild type mice. By offering temporally precise control of specified ligand-receptor interactions in neurons, this approach may facilitate molecular neuroscience studies in behaving organisms.