Rubuta ci gaba don wannan sakin layi - Johnston ya fara bugawa Munster wasa a ranar 5 ga Satumba, 2015, yana farawa a wasan farko na 2015 <unk> 16 Pro12
a kan 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.