Members of Friends of Broadwater and Worthing Cemetery spotted the discovery during a voluntary clean-up.
Items inside the bag included Tiffany bracelets, Sekonda watches and Elements items.
The group have handed it into the police station.
John Vaughan, media officer for the group, told the Herald: “On the last Saturday of every month throughout the year the Friends of Broadwater and Worthing Cemetery attend a two-hour cemetery clearance and maintenenance session where they prune tress, trim shrubs and bushes, cut down brambles and re-discover long lost grave headstones.
“This morning, 17 members attended to keep this 14.5 acre Worthing ‘oasis’ in good shape.
“Towards the end a large clump of ivy was being trimmed back when we discovered a bag placed or perhaps hidden in the undergrowth.
“With some caution the bag was removed and the contents examined. It appeared that there were a number of jewellery boxes in the bag and it soon became apparent that the bag was full of jewels.
“Although ‘bottom end’ of the market items and some costume jewellery were present there were Tiffany bracelets, Sekonda watches and Elements items, earings, bracelets, rings, necklaces, a cameo brooch and many other items.
“Clearly some thief had quickly disposed of his ill gotten gains and had used the undergrowth as a hiding place, or he or she may have extracted the most valuable items and disposed of the rest.
“The find caused much excitement and one friend uttered that he would ‘take the items to the police immediately following his round the world cruise’.”
The public are welcome to attend the group’s maintenance days, at 10am on the last Saturday of every month, meeting by the cemetery chapels.
Mr Vaughan added: “You never know what you are going to find; last month it was rugby and footballs kicked into the cemetery from the adjacent school.”