Method for well re-stimulation treatment using instantaneous shut-in pressure (ISIP) to guide the design and execution of refracturing stages. Pore pressure and optional cluster stresses are determined at a start of the treatment. Goal ISIPs for the refracturing correspond to undepleted regions of the formation, and target ISIPs versus treatment progression/stage range from about a lowest pore pressure corresponding to depleted regions of the formation up to within the goal range ISIPs. Diversion and proppant pumping schedules are designed, and the refracturing treatment is initiated in accordance with the design. ISIP is measured at stage end, and if it varies from the target ISIP, subsequent stages are modified from the design as needed to more closely match the ISIP schedule.