In September 1777, Dearborn was transferred to the 1st New Hampshire Regiment, under Colonel Joseph Cilley. He took part in the Saratoga campaign against Burgoyne at . The first battle was largely fought by troops from New Hampshire, Dearborn's home state. The New Hampshire brigade under General Poor and a detachment of infantry under Major Dearborn, numbering about three hundred, along with detachments of other militia, and Whitcomb's Rangers, co-operated with Morgan in the repulse of Fraser's attack. The cautious General Horatio Gates reluctantly ordered a reconnaissance force consisting of Daniel Morgan's Provisional Rifle Corps and Dearborn's light infantry to scout out the Bemis Heights area. Gates later noted Dearborn's marked ability as a soldier and officer in his report. Thereafter Dearborn joined General George Washington's main Continental Army at Valley Forge, Pennsylvania, as a lieutenant colonel, where he spent the winter of 1777–1778.