This paper is based on the master's thesis of the first author. Objectives: This study investigated whole-word phonological characteristics and articulation error types through nonword repetition under different phonetic complexity to examine the effect of phonetic complexity on phonological characteristics and articulation error frequencies. Methods: Forty-five typically developing children aged 4-5 participated as subjects and were divided into three group: early 4 years old, late 4 years old, and early 5 years old. A repetition task using 50 nonwords was performed with the respective groups to investigate inter-and intra-group differences in whole-word analysis indexes and frequencies of articulation error by type according to phonetic complexity scores (low/high). Results: Significant differences were found in the whole-word analysis indexes between age groups and phonetic complexity. The interaction effects of phonetic complexity and age group were also significant. Significant differences were found between the early 4 years old and late 4 years old, and between early 4 years old and early 5 years old. Differences between late 4 years old and early 5 years old were significant in word correctness, whereas a difference among age groups was not found in word variability of nonwords with low phonetic complexity. Frequency of articulation error by type was higher for nonwords with high phonetic complexity. Articulation error by type occurred most frequently among the early 4 years old. As for articulation error by type, substitution occurred most frequently, followed by omission and addition. Conclusion: Results supported the previous studies suggesting that articulation error frequency is higher for nonwords with high phonetic complexity, and thus indicated the necessity for word selection allowing for phonetic complexity when conducting clinical phonological assessment and intervention.