Newcastle went ahead on three minutes when Damien Duff latched on to an error by Paul Arnison to slot past keeper Tom Woodhead.
Darlington levelled within three minutes when Dean Windass converted a penalty after Tamas Kadar’s trip on Mark Convery.
Kevin Nolan restored United’s lead on 17 minutes with a simple chance, and Shola Ameobi’s neat control allowed him to make it 3-1 from close range 11 minutes later.
Ameobi added a fourth with a fine finish from a tight angle nine minutes before the break and Jonas Gutierrez made it five on 47 minutes.
Steven Taylor netted with a header and although Windass pulled one back with 24 minutes left, Andy Carroll thumped home Jose Enrique’s cross to make it 7-2.