After explaining why consideration of the use of technology in second language (L2) teaching in the primary and secondary sectors is necessary, this systematic review presents a keyword map of 117 papers that have researched technology in L2 learning since 1990. It reveals that research effort has increased, in these educational phases, in line with technological developments and that there have been important differences in the adoption of applications between the primary and secondary sectors. We then provide an in-depth review of 47 post-2000 studies which investigate the efficacy of technology in the teaching of L2 English. We ask what technology has been used in the new century and why, what evidence there is that technology facilitates language learning, and what other insights can be drawn from the research in this field. The evidence that technology has a direct beneficial impact on linguistic outcomes is slight and inconclusive, but it may impact indirectly and positively by changing learner attitudes and learning behaviours and may promote collaboration. However, the research surveyed does not differentiate these positive impacts by group differences (e.g. gender). On the whole the research reviewed lacked the quality that would reassure practitioners and policy-makers that technological investment is warranted. We argue that future research needs to provide a tighter link between technological applications, Second Language Acquisition (SLA) theory, and learning outcomes.