Taimoor Raza was found guilty of insulting the prophet Mohammed after an argument on Facebook with a counter-terrorism department official.
A Pakistani man has been sentenced to death for committing blasphemy on Facebook, lawyers said on Saturday, the first conviction on charges arising from social media.
Judge Shabbir Ahmad Awan handed down the verdict in Bahawalpur, around 600 km ( 372 miles) south of capital Islamabad, finding Taimoor Raza guilty of insulting the Prophet Muhammad, prosecutor Shafiq Qureshi said.
Raza had a Facebook argument about Islam with someone who turned out to be a counter-terrorism department official, defence lawyer Rana Fida Hussain said.
The official brought charges against Raza based on the comments made on the social networking site.
Hussain said his client was innocent and that he would appeal the conviction.
Controversy over the blasphemy law has exposed the growing gap between hard-line religious conservatives and liberals in Pakistan.
More than 100 people are charged with blasphemy and jailed each year in the country. Critics say even unproven allegations can trigger mob lynching and violence.
A 10-year-old boy was killed and five others were wounded last month when a mob attacked a police station in an attempt to lynch a Hindu man charged with blasphemy for allegedly posting an incendiary image on social media.
Millions of Pakistanis have been receiving text messages from the government warning them against sharing "blasphemous" content online, a move rights activists said would encourage more vigilante attacks.