The Championship leaders have now lost more matches at home than they have away (three) this season. The defeat made sure Brighton and Hove Albion caught up with them on top of the table following their 3-0 win against Derby County on Friday, but the Magpies have a better goal difference.
The visitors raced into an early lead via Tom Cairney in the 15th minute before Sessegnon scored a second-half brace, with Nigerian Sone Aluko assisting both times.
Making his 10th start of 24 appearances all season, Atsu then assisted Daryl Murphy for a consolation goal on 76 minutes.
Youngster Sessegnon had an opportunity to score a hat trick when he was brought down in injury time but his American teammate Tim Ream sent the resulting penalty wide.
With nine matches left this season, Rafa Benitez’s men need to maintain their focus if they are to succeed in shaking off the challenge of Brighton for the title. They remain six points ahead of Huddersfield in third place as the race for promotion to the Premier League heats up.