Neuvirth, playing in just his second NHL contest, was bombarded by six shots in the final five minutes of the third period -- including Todd White's unassisted goal at the 18:03 mark -- but in the end, he came away with his second victory.
Alexander Semin led Washington with a goal and two assists. Mike Green had a goal and a assist, while Brooks Laich (power play) and Eric Fehr both scored once in the Capitals' franchise-record 10th straight sellout.
Green's second period goal gave him 23, an NHL-high among defensemen.
Atlanta's other goals were scored by Ilya Kovalchuk in the first and Rich Peverley in the second.
Kari Lehtonen was beaten four times on 40 shots in the Thrashers' third straight loss at the Capitals' Verizon Center.
Washington's Viktor Kozlov returned from a nine-game injury absence (groin).