The magnetic field effects on the decay kinetics for chain-linked triplet biradicals have been observed by the use of a laser photolysis apparatus with a conventional electromagnet and a pulsed magnet. Biradical lifetimes increase steeply to their maxima from the zero field to ca. 2 T. The biradical decay times tend to decrease gradually with further increase of the magnetic field intensity to 14 T. The decreased lifetimes for triplet biradicals can be explained in terms of spin-lattice relaxation due to hyperfine anisotropy and to g tensor anisotropy.