A process for the preparation of exametazime (formula I), which comprises the steps of: a) reacting 2,3-butanedione monoxime (formula II) with 2,2-dimethyl-1,3-propanediamine (formula III), in a suitable solvent, in presence of dehydrating agent to afford diimine derivative 4,8-diaza-3,6,6,9-tetramethylundecane-3,8-diene-2,10-dione bisoxime (formula IV); wherein the dehydrating agents is selected from calcium hydride, molecular sieves, magnesium sulphate and sodium sulphate; b) reducing diimine derivative 4,8-diaza-3,6,6,9-tetramethylundecane-3,8-diene-2,10-dione bisoxime (formula IV) with a suitable reducing agent in a suitable solvent to afford a mixture of 'd', 'l' and meso isomers; c) treating the mixture of 'd', 'l' and meso isomers with d or l chiral resolving acid to form the corresponding acid addition salts and separating said one of the enantiomers of exametazime as acid addition salt; d) treating the mother liquor of step (c) with a suitable base; e) isolating a mixture of 'd' or 'l' enantiomer and meso isomer; f) purifying the mixture obtained in step (e); g) treating the mixture from step (f) with l or d chiral resolving acid to form the corresponding acid addition salts and separating said other enantiomer of exametazime as an acid addition salt; h) mixing the acid addition salt of step (c) and step (g) and; i) treating the mixture of acid addition salts of step (h) with a suitable base to afford Exametazime. j) wherein the chiral resolving acid is selected from L-(+) tartaric acid, D-(-) tartaric acid, L-malic acid, D-malic acid, S-(+) mandelic acid, R-(-) mandelic acid, S-(+)-O-acetyl mandelic acid, R-(-)-O-acetyl mandelic acid, (-)-naproxen, (+)-naproxen, -(-)-camphor sulfonic acid, -(+)-camphor sulfonic acid, -(+)-bromocamphor-10-sulfonic acid, -(-)-bromocamphor-10-sulfonic acid, (-)-Dibenzoyl-L-tartaric acid, (-)-Dibenzoyl-L-tartaric acid monohydrate, (+)-Dibenzoyl-D-tartaric acid, (+)-Dibenzoyl-D-tartaric acid monohydrate, (+)-dipara-tolyl-D-tartaric acid, (-)-dipara-tolyl-L-tartaric acid, L(-)-pyroglutamic acid, L(+)-pyroglutamic acid, (+)-lactic acid, (-)-lactic acid, -(+)-2-chloromandelic acid, -(-)-2-chloromandelic acid. a) reacting 2,3-butanedione monoxime (formula II) with 2,2-dimethyl-1,3-propanediamine (formula III), in a suitable solvent, in presence of dehydrating agent to afford diimine derivative 4,8-diaza-3,6,6,9-tetramethylundecane-3,8-diene-2,10-dione bisoxime (formula IV); wherein the dehydrating agents is selected from calcium hydride, molecular sieves, magnesium sulphate and sodium sulphate; b) reducing diimine derivative 4,8-diaza-3,6,6,9-tetramethylundecane-3,8-diene-2,10-dione bisoxime (formula IV) with a suitable reducing agent in a suitable solvent to afford a mixture of 'd', 'l' and meso isomers; c) treating the mixture of 'd', 'l' and meso isomers with d or l chiral resolving acid to form the corresponding acid addition salts and separating said one of the enantiomers of exametazime as acid addition salt; d) treating the mother liquor of step (c) with a suitable base; e) isolating a mixture of 'd' or 'l' enantiomer and meso isomer; f) purifying the mixture obtained in step (e); g) treating the mixture from step (f) with l or d chiral resolving acid to form the corresponding acid addition salts and separating said other enantiomer of exametazime as an acid addition salt; h) mixing the acid addition salt of step (c) and step (g) and; i) treating the mixture of acid addition salts of step (h) with a suitable base to afford Exametazime. j) wherein the chiral resolving acid is selected from L-(+) tartaric acid, D-(-) tartaric acid, L-malic acid, D-malic acid, S-(+) mandelic acid, R-(-) mandelic acid, S-(+)-O-acetyl mandelic acid, R-(-)-O-acetyl mandelic acid, (-)-naproxen, (+)-naproxen, -(-)-camphor sulfonic acid, -(+)-camphor sulfonic acid, -(+)-bromocamphor-10-sulfonic acid, -(-)-bromocamphor-10-sulfonic acid, (-)-Dibenzoyl-L-tartaric acid, (-)-Dibenzoyl-L-tartaric acid monohydrate, (+)-Dibenzoyl-D-tartaric acid, (+)-Dibenzoyl-D-tartaric acid monohydrate, (+)-dipara-tolyl-D-tartaric acid, (-)-dipara-tolyl-L-tartaric acid, L(-)-pyroglutamic acid, L(+)-pyroglutamic acid, (+)-lactic acid, (-)-lactic acid, -(+)-2-chloromandelic acid, -(-)-2-chloromandelic acid.