In December 1807, Harispe was made chief of staff of the Corps of Observation of the Ocean Coast under the orders of Marshal Moncey. With this corps, he partook in the Spanish campaign of 1808. In November 1808, Harispe fought under Marshal Lannes at the Battle of Tudela and in the siege of Saragossa. After Lannes returned to France on the outbreak of the War of the Fifth Coalition, Harispe became chief of staff to general Suchet.