A flexible approach prepares amino-functional graphene aerogels with different additions of carbon nanotubes (CNTs) for use as an adsorbent to study the adsorption performance of formaldehyde in indoor air. Experimental results indicated that the decoration of amino groups offers a greater number of chemical adsorption sites, which mainly contributed to the improvement of the chemical adsorption capacity of graphene aerogels, and the breakthrough time increased from 0 to 390 min g–1 under 3.7 ppm of formaldehyde. The addition of CNTs can significantly enhance the adsorption properties. More interestingly, the breakthrough time presents a substantial increase from 390 to 20,300 min g–1 when the mass ratio of CNTs and graphene increased from 0:1 to 2:1 and then decreased to 18,000 min g–1 at the ratio of 3:1. The addition of CNTs weakens the agglomeration degree and achieves a greater number of adsorption sites by playing a supportive and connective role among graphene sheets. However, more CNTs will agglomerate, and fewer functional groups on the surface limit additional amounts. The adsorption mechanism was also studied by analyzing the surface specific area and N content. This work provides new insights into the application of amino-functional graphene aerogels with the additions of CNTs (AGCAs) as a potential adsorbent to eliminate indoor formaldehyde pollution.