In 2013, Manumalealii was named in the Samoa squad for the World Cup.[11] He scored a try in their opening match against New Zealand.
In May 2014, Penani played for Samoa in the 2014 Pacific Rugby League International. He scored three tries in Samoa's 32-16 victory. He dedicated those tries to his mother who had died months earlier.[12]
On 8 September 2014, Manumalealii was selected for the Samoa Four Nations train-on squad.[13] On 7 October 2014, Manumalealii was selected in the Samoa national rugby league team final 24 man squad for the 2014 Four Nations series.[14][15]