Nonpolymer, pH-sensitive carbon dots (pSCDs) were developed to overcome the disadvantages of pH-sensitive polymers such as inevitable synthesis, wide distribution of molecular weight, uncontrolled loading and release rate of drugs, and toxicity by biodegradation. The pSCDs were synthesized via one spot synthesis for 3 min using citric acid (CA) and 1-(3-aminopropyl) imidazole (API). Imidazole groups were present on pSCD surfaces and facilitated DOX loading via hydrophobic interactions (loading efficiency: 78.55%). The DOX-loaded pSCDs collapsed at tumoral pH (pH ∼ 6.5) due to protonation of the imidazole groups, and DOX was released about 7 times higher than the control group. The therapeutic effect was confirmed in vitro using HCT-116 (human colon cancer), PANC-1 (human pancreatic cancer), and SKBR-3 (human breast cancer) cells. Additionally, the DOX-loaded pSCDs successfully inhibited tumor growth in an HCT-116-bearing mouse model and did not show toxicity. These results indicate that a nonpolymeric pSCDs platform has the potential to be used as a cancer targeting therapeutic material.