Two women were among the dead at a Methodist church in the restive southwestern city of Quetta in Balochistan province, said provincial Home Secretary Akbar Harifal.
Several of the wounded were in serious condition, police added.
Officials said security forces intercepted and shot one bomber outside but the second attacker managed to reach the church's main door where he blew himself up.
"Police were quick to react and stop the attackers from entering into the main hall," provincial police chief Moazzam Jah told AFP.
Balochistan provincial home minister Sarfraz Bugti said around 250 people normally attend the church on Sundays, but the congregation had swelled to around 400 because it was close to Christmas.
"God forbid, if the terrorists had succeeded in their plans more than 400 precious lives would have been at stake," tweeted the home minister.
An AFP reporter at the scene saw shattered pews, shoes and broken musical instruments littered across the blood-smeared floor of the church.
No group has claimed the attack.