The purpose of this descriptive study was to determine the hopelessness and depression levels of parents of children diagnosed with cancer and undergoing cancer treatment and factors affecting these levels. The study was carried out with parents of 44 children receiving treatment in a paediatric haematology clinic of a university hospital. Data were collected using a survey form, the Beck Hopelessness Scale (BHS) and the Beck Depression Scale (BDS). The mean BDS score of the mothers and fathers was $18.3{pm}11.30$ and $15.2{pm}11.33$, respectively. The mean BHS score of the mothers was $6.45{pm}4.40$, whereas the mean BHS score of the fathers was $5.88{pm}4.27$. The results showed that the levels of hopelessness and depression among the mothers were higher than among the fathers (p<0.001). There was a positive relationship between the hopelessness and depression scores of the mothers and the fathers (p<0.05), and the levels of hopelessness and depression scores of the fathers increased as those of the mothers increased. A weak financial situation of the family increased the hopelessness and depression levels of the fathers. The hopelessness and depression levels of the mothers who were supported by their families and relatives were decreased compared to those without such support (p<0.05). The results show that the parents of children with cancer face many psychosocial and spiritual problems. Using simple screening tools, nurses can identify at-risk parents and direct them to support services. We conclude that actively encouraging families to avail themselves of support resources and supporting them financially would positively affect the levels of depression and hopelessness of parents of children with cancer.