Targeting neuroinflammation is a promising strategy for developing treatments for neurodegenerative diseases. Cyclic nucleotides like cAMP and cGMP, crucial second messengers in the central nervous system. Phosphodiesterases (PDEs) are the sole enzymes that hydrolyze these nucleotides in vivo. Among them, PDE4-specific hydrolysis of cAMP and PD5-specific hydrolysis of cGMP. We hypothesized that simultaneous inhibition of PDE4 and PDE5 could provide superior therapeutic effects. This hypothesis was tested by combining Rolipram (PDE4 inhibitor) and Tadalafil (PDE5 inhibitor), evaluating their impact on cAMP, cGMP, and inflammatory factors in LPS-induced BV2 cells and APP/PS1 mice, along with cognitive effects in the mice. Additionally, a novel dual-target PDE4/5 inhibitor, C-3-1, was designed, synthesized, and evaluated for its ability to regulate neuroinflammation and improve cognitive functions. RNA sequencing identified gene expression changes and pathway alterations. Our findings indicated that dual inhibition of PDE4 and PDE5 synergistically improved neuroinflammatory responses and cognitive functions. C-3-1 also reduced the activation of microglia and astrocytes and increased neuron numbers. The anti-neuroinflammatory effects of C-3-1 are achieved by affecting NF-κB and JNK pathways, highlighting the potential of multitargeted therapy in neuroinflammation treatment. This research supports the development of combined PDE4/5 inhibitors as effective therapeutic agents for neurodegenerative diseases.