In front of 2,773 at Gateshead International Stadium, Katie Kitching scored the only goal of a bitty and bad-tempered affair - while Martha Thomas saw a second-half penalty kept out by Noa Schumacher.
Jordan Nobbs forced a save from Schumacher in the opening seconds, then the team's top scorer Thomas flashed an effort across goal in the ninth minute.
Moments later, Katie Bradley did brilliantly to release Beth Lumsden, who played in Nobbs, but her effort was parried by the Sunderland goalkeeper.
Schumacher was called into action again when Jemma Purfield poked a low Lumsden cross goalwards, but it lacked the power to trouble the American shot stopper.
The remainder of the first half was low on incident but the second period began with a bang when Sunderland substitute Katy Watson burst past Charlotte Wardlaw and helped the ball into the path of Kitching, who placed an effort beyond Kayla Rendell.
Newcastle were awarded a penalty in the 65th minute when Nobbs raced onto Rachel McLauchlan's pass down the line and went down under Schumacher's challenge - although the goalkeeper was insistent that she got a touch on the ball.
She certainly got hands to Thomas' spot-kick, though, diving low to her right to push it away.
At the other end, Rendell made a good save to repel a Mary Corbyn effort before, in the 85th minute, a Freya Gregory cross-shot was palmed out by Schumacher.
Newcastle have won five out of five in Barclays Women's Super League 2, but by contrast have now lost both of their cup matches - and face Everton Women in the same competition at Goodison Park on Wednesday evening.
Newcastle United Women: Kayla Rendell, Charlotte Wardlaw, Jordan Nobbs, Jemma Purfield, Mollie Lambert (Kathleen McGovern 60), Hildur Antonsdóttir (Freya Gregory 60), Martha Thomas, Katie Bradley (Lois Joel 81), Aoife Mannion, Beth Lumsden (Leanne Kiernan 67), Rachel McLauchlan (c)
Subs not used: Anna Tamminen, Hanna Németh, Oona Sevenius, Gemma Evans, Jessie Gale




