Marshall Ball gave the Marigolds a first-half lead and player-joint-boss George Gaskin doubled i ten minutes from time. Sheppey pulled one back but Matt Storm made the result safe with a late third.
It lifts them above Lancing and up to 18th ahead of a visit to Phoenix, who are just below them, next Saturday.
See pictures by Stephen Goodger from the victory on this page and those linked. Get all the local football in the Worthing Herald and Littlehampton Gazette, out on Thursday.
1. Littlehampton Town v Sheppey United pictures by Stephen Goodger (4).jpeg
Littlehampton Town v Sheppey United, Isthmian south east division Photo: Stephen Goodger
2. Littlehampton Town v Sheppey United pictures by Stephen Goodger (8).jpeg
Littlehampton Town v Sheppey United, Isthmian south east division Photo: Stephen Goodger
3. Littlehampton Town v Sheppey United pictures by Stephen Goodger (3).jpeg
Littlehampton Town v Sheppey United, Isthmian south east division Photo: Stephen Goodger
4. Littlehampton Town v Sheppey United pictures by Stephen Goodger (2).jpeg
Littlehampton Town v Sheppey United, Isthmian south east division Photo: Stephen Goodger