CoCl 2(TPPTS) 2 catalyzed hydroformylation of 1-octene and 1-decene was studied in an aqueous biphasic medium. The effect of temperature, pressure and addition of cetyltrimethylammonium bromide (CTAB) and tri( m-sulfophenyl)-phosphine (TPPTS) in the reaction mixture on the hydroformylation of alkenes was investigated. Increase in conversion of 1-octene and 1-decene with higher aldehyde selectivity was observed in the presence of CTAB. The leaching of cobalt complex, CoCl 2(TPPTS) 2, from aqueous phase to organic phase in presence of TPPTS was observed to decrease. There was slight decrease in the conversion on increasing the TPPTS to cobalt molar ratio. The addition of CTAB increases the conversion (95%) and selectivity (90–95%) for aldehyde whereas the addition of TPPTS facilitates the separation of organic–aqueous phase. Hydroformylation was also studied in the presence of ethanol and methanol under the optimum reaction conditions.