Kammala jumla mai zuwa: Johnston ya fara bugawa Munster a ranar 5 ga Satumba, 2015, yana farawa a wasan farko na
2015<unk>16 Pro12 da Benetton. A watan Janairun 2016, an sanar da cewa Johnston ya sanya hannu kan kwangila tare da Munster wanda zai gan shi ya shiga manyan 'yan wasa daga kakar 2016-17, da farko a kan kwangilar ci gaba sannan kuma, daga 2017-18, a kan cikakken kwangila. An zabi Johnston don Kyautar 'Yan wasan Kwalejin Munster na 2016.