Recently, flexible metacomposites with negative permittivity have triggered extensive interest owing largely to their promising applications in areas such as sensors, cloaking, and wearable and flexible electronic devices. In this paper, flexible silver nanowire/carbon fiber felt (AgNW/CFF) metacomposites with weakly negative permittivity were fabricated by adjusting their composition and microstructure. Along with the formation of a conductive AgNW network, the resulting composites gradually presented metal-like behavior. Interestingly, weakly negative permittivity with a small absolute value (as low as about 6.4) and good flexibility were observed in the composites with 3.7 wt% AgNWs. The one-dimensional silver nanowires contribute to reducing the overall electron density of the resulting composites, which is responsible for the weakly negative permittivity. As the AgNWs increased, the Drude-like negative permittivity got stronger owing to the enhancement of the electron density. Further investigation from the perspective of microelectronics revealed that the negative permittivity is dependent on the inductive characteristic. The proposed design strategy for AgNW/CFF composites with tunable negative permittivity opens up a new approach to flexible metacomposites.