Though Resaca was a tactical victory for Johnston, he was unable to maintain his position once Sherman began to threaten his supply line and was forced to withdraw.

Sherman's Union troops lost a lot of soldiers during the Battle of Resaca, while inflicting comparably few casualties on Confederate forces, and made no real progress during the battle. Even though the Union army suffered a dismal outcome, the combat succeeded in its aim of diverting Johnston and his troops from the Union's attempts to cross the Oostanaula River at Lay's Ferry. It would only have been a matter of time before Johnston's supply line at Resaca was cut once Sweeny and his division crossed, clearing the way for reinforcements.

Without supplies, the Confederate line would not have been able to defend itself against the attacking Federals. When Johnston learned about the crossing, he was eventually forced to leave. Confederate troops started to evacuate in the late afternoon of May 15; however, some skirmishers stayed, firing guns and creating enough noise so Union forces would not detect a retreat. Johnston had left Resaca by 3:30 a.m. on the 16th, and Confederates had set fire to the rail line.