Missing injured skipper Craig Morgan and with loan signings James Chester and Lee Frecklington picking up knocks in training, it was always going to be to tough at the back for Posh. And the problems for Darren
Ferguson's side multiplied when stand-in centre back Charlie Lee limped off after just 18 minutes.
It went from bad to worse as Posh twice conceded from set-pieces in the space of three minutes. Paul Warne forced the ball home to put Yeovil ahead from close range after Alex Prijovic flicked on a 31st minute corner by
Andy Welsh. And Welsh caused problems again with a 33rd minute free-kick that Aaron Brown turned to net with the outside of his left-foot.
George Boyd shot tamely when Posh finally carved out an opening and Aaron McLean twice went close at the end of the first-half, sending a right-foot shot wide and then they saw a firm header from a Danny Blanchett centre blocked by Jon Worthington.
McLean did better on 56 minutes grabbing his 15th goal of the season, converting a Boyd pass after a strong run by substitute Chris Whelpdale and with the Yeovil goal under siege for a spell, goalkeeper Josh Wagenaar handled impressively under pressure.
Hopes of a Posh revival were dashed with a 69th minute schoolboy howler from goalkeeper Joe Lewis who punched a Shaun MacDonald shot into his own net to restore a two goal lead. Yeovil went on to end a Posh unbeaten home league run of 13 matches.