A microwave-assisted, environmentally friendly, high-yielding, time-saving synthesis of medicinally important 3-substituted isocoumarins was carried out in a single step by direct condensation of homophthalic acid with aryol and acyl chlorides under solvent-free conditions without any solid support. The synthesised isocoumarins were structurally characterised by microanalysis, 1H NMR, EI, IR and UV.