The Trends in International Mathematics and Science Study (TIMSS) was administered via computer, eTIMSS, for the first time in 2019. The purpose of this study was to investigate item block position and item format effect on eighth grade mathematics item easiness in low- and high-achieving countries of eTIMSS 2019. Item responses from Chile, Qatar, and Malaysia which were low-achieving countries as well as Republic of Korea, Chinese Taipei, and Singapore which were high-achieving countries, were used in the study. The block position and item format effects were investigated within explanatory item response theory framework. The results revealed that there was a negative and statistically significant item block position effect in all low-and high-achieving countries, and it is more prominent in the low-achieving countries. As item block increased, students' probability of giving a correct response to an item decreased. Additionally, the results showed that all high- and low-achieving countries had a negative and significant item format effect in that multiple-choice items appeared easier compared to constructed response items.