This communication reports about heat shock protein response after arsenic exposure in broiler chickens in vivo and in vitro both. Splenocytes harvested in presence of sodium arsenite expressed Heat shock protein 70 (HSP 70) which could be identified on the basis of relative migration pattern and western blot analysis. Serum levels of HSP 70 in broiler chicken also increased after continuous feeding of sodium arsenite in drinking water. This particular observation may be attributed towards systematic inflammation, oxidative stress and hepatocellular injury. In vitro relative quantification of transcription level of HSP 70 revealed that splenocytes harvested in presence of sodium arsenite expressed (final concentration 3 and 7 μM/ml) more HSP 70 in comparison to cells harvested without sodium arsenite and the values were statistically significant (P < 0.001) when compared to untreated control. Collectively this result indicated that, HSP 70 level increased both in vivo and in vitro trials and may be used as potential molecular and toxicological biomarker.