A fuel nozzle assembly and a gas turbine combustor including the same are provided. The fuel nozzle assembly may include an end plate coupled to one end of an annular casing, and a fuel nozzle configured such that one end thereof is supported by the end plate and the other end thereof extends outward. The fuel nozzle may include a center fuel nozzle and a plurality of side fuel nozzles arranged annularly to surround the center fuel nozzle. The side fuel nozzle may include a nozzle body located at a center thereof, a shroud spaced outward from the nozzle body, and a plurality of swirlers located between the nozzle body and the shroud. Each of the swirlers may include a leading edge directed toward the end plate and a trailing edge located opposite the leading edge. In each of the side fuel nozzles, distances between the leading edges are different from each other.