Feedback control algorithms, an important tool in climate intervention strategy design, are widely used in stratospheric aerosol injection (SAI) simulations but have never been implemented for marine cloud brightening (MCB). Using the Community Earth System Model (CESM2), we present the first simulations of feedback control-regulated MCB. Our controller, which regulates global mean temperature (T0) by varying the area of MCB coverage over time, successfully maintains the desired T0 of 1.5°C above the preindustrial in the SSP2-4.5 global warming scenario comparably to a contemporary SAI controller. After 35 years of intervention, the surface temperature response when MCB has been gradually ramped up over time in this way is similar to a constant intervention with similar global mean temperature (including strong regional heterogeneity), but system memory may cause differences in Arctic sea ice and the Atlantic Meridional Overturning Circulation (AMOC).