Crews spent around three hours tackling, and then damping down, the blaze.
Guernsey Fire and Rescue say Green Watch were called to Mont Cuet at around 8 last night, Bank Holiday Monday, (6 April).
An area of 30 metres by 10 metres was on fire and they used four main jet hoses to tackle it.
Staff from the site were called and they used a digger to turn over the waste, so the hoses could be concentrated on the fire's hearth.
People were told to keep away from the area during the incident.
Crews say the fire was out by just after 11pm.
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