Fenugreek (Trigonella foenum-graecum L.) has a long and respected history of medicinal uses in Middle East and Persian medicine. The hypocholesterolaemic and hypoglycaemic effects of fenugreek were attributed to its major steroidal sapogenin, diosgenin and its major alkaloid, trigonelline. The knowledge of diosgenin and trigonelline biosynthesis is derived from studies of cholesterol and nicotinic acid production through acetyl-CoA→ mevalonate→ isopentenyl pyrophosphate→ squalene→ lanosterol→ cholesterol→ diosgenin and quinolinic acid→ nicotinamide adenine dinucleotide→ nicotinamide→ nicotinic acid→ trigonelline pathways, respectively. This paper reviews the secondary metabolites and metabolic pathways of diosgenin and trigonelline production in fenugreek as a medicinal plant and economical crop.