Premiership outfit Charlton survived a major scare at Grimsby as they edged into the Carling Cup third round.
Danny Murphy put the Premiership side ahead after seven minutes when he curled home an inch-perfect free-kick.
Grimsby refused to be cowed and the hosts created a handful of glorious chances, but they were unable to find a way past Charlton keeper Dean Kiely.
Jeffers wrapped things up with a decisive right-foot finish after being set up by substitute Kevin Lisbie.
Grimsby: Anthony Williams, Whittle, Young, Gordon, McDermott,
Pinault (Coldicott 85), Fleming, Crowe (Bull 75),
Sestanovich (Hockless 84), Reddy, Parkinson.
Subs Not Used: Robinson, Marcelle.
Charlton: Kiely, Young (Kishishev 45), Perry,
Fortune (Euell 57), Hreidarsson, Stuart, Murphy, El Karkouri,
Hughes, Johansson (Lisbie 69), Jeffers.
Subs Not Used: Rommedahl, Royce.
Goals: Murphy 8, Jeffers 79.
Ref: A Marriner (W Midlands).