The Tasmanian was last down the ramp for the final 35 kilometre ITT with teammate Stefan Küng's time of 39 minutes and 44 seconds the one to beat.
The new father came home a minute and four seconds slower than the current Swiss national TT champion but was untroubled by his nearest rivals.
Astana's Jakob Fuglsang blitzed the race against the clock beating Porte home by 26 seconds and earned him enough time to leapfrog Nairo Quintana (Movistar) to second on GC. The Colombian finished the ITT 55 seconds behind Porte.
"I've won at races like Paris-Nice, Volta Catalunya and Tour de Romandie,' Porte said.
"But this race is so special and to come here after the passing of Andy Rihs earlier in the season and win his home Tour is a massive satisfaction. I dedicate this win to Andy."
"Let's not beat around the bush. It's a very important race and I think it's disrespectful to say it's a 'lead in' race for the Tour de France as it means a lot to win it. It's such a prestigious race.
"So, I think going forward into the Tour de France, it's a good sign to win here. Before this race, I hadn't raced since Tour de Romandie. I was at home for the birth of my son two weeks ago and I've only had one night at home with him so, I think it's great for me to get to go home for a bit of time before a training camp and then hopefully I'll be better at the Tour de France."
Australia's Michael Matthews (Sunweb) finished the ITT in a strong fifth position, his valiant efforts earning him two more sprint points to tie with Peter Sagan (Bora-hansgrohe). But the Canberran agonisingly lost out to the world champion after a countback.