Changes in microbial characteristics in soils with increasing salinity were measured in 30 soil samples belonging to Kattikhel and Dargai soil series occuring in Khyber Pakhtunkhwa of North West Pakistanduring 2009. Microbial characteristics including microbial biomass C, microbial biomass N, C/N ratio in microbial biomass, N mineralization, nitrification, rate of CO2 evolution and cumulative CO2 production were measured. The soils used in the study were alkaline in reaction and had electrical conductivity (EC) gradient from 0.63-32.3 dS m-1. All microbial indices showed a decreasing trend with increasing EC. The average microbial biomass C of soils decreased from 391 mg kg-1 in soils with EC of <4.0 dS m-1 to 209 mg in soils with EC of >12 dS m-1. The same trend was observed for microbial biomass N, N mineralization, nitrification, rate of CO2 evolution and cumulative CO2 production with respect to elevated EC. The C/N ratio of soil microbial biomass increased with increasing salinity. These results suggested that soil microbial biomass were highly sensitive to salinity and can be used as indicator for management of salt affected soils.