Incremental synthesis for changes to a circuit design can include synthesizing, using computer hardware, a first circuit design resulting in a partitioning of the first circuit design and a plurality of synthesized partitions of the first circuit design and, for a second circuit design that is a modified version of the first circuit design and based upon the partitioning of the first circuit design, determining, using the computer hardware, a partition of the second circuit design that differs from the first circuit design. The partition of the second circuit design can be technology mapped using the computer hardware resulting in a synthesized partition of the second circuit design. A synthesized circuit design corresponding to the second circuit design can be generated using the computer hardware by combining synthesized partitions of the plurality of synthesized partitions of the first circuit design that are unchanged relative to the second circuit design with the synthesized partition of the second circuit design.