Many　practical　systems　need　to　fulfill　their　mission　in　multiple　phases,　where　the　system　in　different　phases　may　have　to　perform　different　tasks　undergoing　different　environmental　conditions　and　success　criteria.　In　the　last　few　decades,　reliability　modeling　and　evaluation　of　phased　mission　systems　(PMSs)　and　related　optimization　problems　have　attracted　a　lot　of　attention.　This　chapter　is　dedicated　to　a　comprehensive　review　of　recent　developments　on　reliability　evaluation　and　optimization　of　PMSs.　Different　evaluation　methods　are　classified　and　their　applicability　to　different　types　of　PMSs　(e.g.,　static　versus　dynamic;　redundant　versus　non-redundant;　perfect　coverage　versus　imperfect　coverage)　are　discussed.　Traditional　and　recently-developed　optimization　problems　related　to　PMSs　are　introduced.　Some　directions　for　future　researches　are　suggested.　©　Springer　Nature　Singapore　Pte　Ltd　2019.