The purpose of this study was to examine the relationships among homework time, homework frequency, and learning achievements of Taiwanese students. Applying a 2-level hierarchical linear modeling on the TIMSS 2007 and 2011 data, our findings were as follows: (1) Within the context of TIMSS 2007 and 2011 students, the frequency of mathematics homework positively predicted mathematics learning achievements; (2) Within the context of TIMSS 2007 students, the amount of time spent doing mathematics homework positively predicted mathematics learning achievements. (3) Among TIMSS 2011 students, homework time in mathematics of 1 to 15 minutes, 16 to 30 minutes, 31 to 60 minutes, and 61 to 90 minutes all could positively predict mathematics learning achievements of Taiwanese 8th-grade students, except for homework time more than 90 minutes. It revealed that in relation to mathematics homework time, too much homework might be as bad as not enough.