Luis Suarez and Edinson Cavani each passed up opportunities to clinch the points against a Pharaohs side who kept Mohamed Salah on the bench, but it was centre-back Gimenez who proved the hero.
After the excitement of Group A rivals Russia's goal frenzy a day earlier, there was a serious lack of invention on show in Ekaterinburg.
Rampant Russia thrash Saudi Arabia in World Cup opener
Suarez missed two golden opportunities as goalkeeper Mohamed El-Shenawy excelled, before Cavani struck the post with a late free-kick, seemingly sealing a point for Egypt on their return to the finals.
But Gimenez rose highest to meet a set-piece and bury a header past El-Shenawy, celebrating a fine end to a week in which he signed a new contract at Atletico Madrid.
Egypt offered little in Salah's absence and are now under pressure heading into a clash with Russia, while Uruguay - and particularly Suarez - can breathe a sigh of relief.
