The 'hosts' in the United Arab Emirates were kept to 96-9 after 20 overs, the Australians chasing down the tally with six overs to spare.
Pakistan's eighth- and ninth-wicket stands were their largest, with 14 and 15 runs respectively, with middle-order bat Saad Nasim (25) the only of the top eight to surpass 10.
Former paceman Younis said they needed to bat for longer, with the World Cup starting in February in Australia and New Zealand.
"Batting, we didn't really put enough runs on the board," Younis said.
"Losing early wickets, it was not easy after that. And full credit to the Australians, they bowled well, they bowled to the plan and they came out good.
"I think there was nothing wrong with the pitch, it just spun a little more than usual.
"The major focus for us is how are we going to deal with 50 overs? We have to make sure that we bat 50 overs. It was disappointing what happened today."
Younis highlighted the poor form of Umar Akmal, the 24-year-old keeper-batsman making one off five, to mark his third consecutive T20I in which he has failed.
"That's not only a worrying sign for U but for us also," Younis said of Akmal.
"We have to really sit down and think hard about his batting, and his wicketkeeping also.
"We speak about his talent. He hasn't really delivered. We have to really speak to him and maybe try different things with him."
The two nations begin a three-match one-day international series in Sharjah on Tuesday.