Introduction Pitch variation, which refers to one's ability to vary fundamental frequency (F0) within or between syllables when speaking, has not been investigated in children with childhood apraxia of speech (CAS). However, pitch variation plays an important role in tone languages, as varying F0 patterns communicate different lexical meanings. This study investigated pitch variation abilities in individuals with CAS via the tone-sequencing tasks (TSTs), focusing on task performance and the effects of syllable structure, lexical status, and tones. Method Three Cantonese-speaking children with CAS (aged 3;7-5;8 [years;months]) and six children without CAS participated in the study. Children without CAS were divided into two control groups, comprising those with speech and/or language impairment or typical development. TSTs consisted of 56 sets of five repetitions of stimuli. The stimuli varied in syllable structure, lexical status, and tones. Percentage of tones correct (PTC), consistency scores, F0 values, and acoustic repetition duration were measured. Results The CAS group performed more poorly than the control groups on the TST with respect to tone accuracy, consistency, and repetition duration. No interaction effects between group and syllable structure or group and lexical status were found. No significant difference was found on F0 values across time between Tone 1 and Tone 2 syllables in the CAS group. However, interaction effects between group and time points of F0 values on Tone 2 syllables were found. Discussion The results suggest that children with CAS have difficulty with pitch variation, which was revealed on the TST with respect to tone accuracy, consistency, and repetition duration. Moreover, children with CAS have difficulty in varying F0 values to produce high-rising tones and tend to use high-level tones to substitute. Clinically, the TST may be useful to assist in the diagnosis of CAS. Isolated vowel stimuli may be useful to test young children or children with severe impairment. Future investigations and development of a normed tool for children with CAS are suggested.