Lung cancer is a lethal solid tumor with poor prognosis because of its high metastasis and resistance to current therapies. Recently, cancer stem cells (CSCs) were suggested to be major contributors to tumorigenicity and cancer relapse. However, therapeutic targets for lung cancer-related CSCs remain undetermined. The objective of the current study was to investigate whether cinnamic acid (CINN) exerts an antitumor activity against sphere-derived lung CSCs. In this study, CSCs were isolated from the non-small cell lung cancer cell line H1299 as tumor spheres under CSC-selective conditions, and found to have increased tumorigenicity, chemoresistance, and higher expression of both embryonic stem cell-related and drug resistance-related genes compared with parental cells. These observations are consistent with the notion that CSCs are tumorigenic, display the ability to self-renew, and generate differentiated progeny that constitute the majority of cells in tumors. Treatment of sphere-derived stem cells with CINN could diminish their CSC-like abilities by decreasing their proliferation and invasive abilities and facilitating their differentiation into CD133-negative cells. Furthermore, CINN treatment increased the sensitivity of CSCs to chemotherapeutic drugs through apoptosis. Of note, xenotransplantation experiments revealed that CINN combined with cisplatin had a synergistic effect in inhibiting the tumorigenicity of CSCs. In summary, our study clearly revealed the presence of a population of sphere-forming cells with stem-like properties among H1299 cells and CINN can attenuate CSC properties of this stem-like cell population. The potential of CINN should be verified further in future studies of anti-CSC therapy.