21st-century learning is integral to the transformation of the curriculum in Malaysia with the transition from School Integrated Curriculum (SIC) to School Standard Curriculum (SSC) introduced around 2014. During this time, the implementation of 21st-century learning was acceptable and very rewarding. However, the impact of implementation on students' skills, abilities, potentials and achievements should be looked at to ensure that the new curriculum is stable and practical to continue. There is a need to discuss the level of metacognitive regulation skills and students' achievement in line with the introduction and implementation of 21st-century learning in the context of the Malaysian curriculum. Therefore, this research was conducted to examine whether the implementation of 21st-century learning has an impact on metacognitive regulation skills and student achievement. This quantitative survey was conducted by 201 Form 2 students from four secondary schools in Pasir Gudang District, Johor, Malaysia. The results show that the level of students' metacognitive regulation skills and the level of achievement in mathematics is moderate. Correlation analysis also showed there was a significant correlation between metacognitive regulation skills and student achievement. The implications from this research suggest that stakeholders including ministries, curriculum developers, education departments and teachers need to take initiatives to strengthen and improve the reputation of curriculum transformation in line with the 21st-century learning era in producing quality education.