New magnetic materials and methods for controlling them are needed to improve data storage technologies. Recent progress has enabled optical detection and manipulation of spins in molecule-based magnets on the femtosecond timescale, which is promising for both increasing the read/write speed but also the data storage density. Experimental developments in femtosecond X-ray free-electron lasers (XFELs) and magneto-optics, in combination with theory advances, have opened up several new avenues to investigate molecule-based magnets. This review discusses the literature concerning ultrafast photoinduced dynamics in Prussian blue analogues (PBAs), which are molecule-based magnets. In PBAs spin–flips and lattice distortions can happen on the 100 fs timescale, which in some analogues lead to photoinduced changes in the long-range magnetic order. The literature and themes covered in this review are of relevance for ultrafast optical control of new multifunctional materials.