Dagenham sunk to the bottom of League Two after Guy Madjo's second-half winner gave Port Vale victory.
The hosts went in front when Brian Woodall connected with Exodus Geohaghon's cross from the right.
But Vale equalised inside a minute when Jennison Myrie-Williams blasted in his 25-yard effort.
After the break Madjo condemned the Daggers to their ninth straight league defeat when he turned home Robert Taylor's cross at the far post.
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Port Vale manager Micky Adams told BBC Radio Stoke:
"We wanted a win to feel better about ourselves and lift the spirits of the football club.
"That's certainly cheered me up, the players and the supporters.
"In the last two games, there's been a real resolve about us, led from Anthony Griffith in midfield, and it's been noticeable."