New Zealand hasn't fielded a sprinter at the world meet since James Dolphin in 2007, also over 200m.
Millar also achieved this time - and fourth national title over the half-lap - without any meaningful opposition, coming off the bend well clear of his rivals, the nearest of which finished more than a second behind.
None of this seemed possible yesterday, when he felt off-colour during qualifying, as he tried to come down off the high of the night before.
"Everything hurt, even my skin hurt. Why, I don't know ... I think it was just the adrenalin and emotion from literally running out of my skin on Friday.
"I woke up this morning with a couple of niggles, but during warm-up, I felt something in my legs and I thought 'let's get this done'.
"But, that good, I wasn't expecting."
Millar may now re-assess his schedule over coming weeks. He has operated at an extremely high level for several weeks now, so he may be better served, with a qualifying time under his belt, to close his campaign down and re-focus on the world championships.
Or he may just have one more crack over 100m at the Australian nationals in two weeks.
Meanwhile, Olympic bronze medallists Eliza McCartney and Tom Walsh - the head-liners for this meet - could not find their best under the blistering heat.
McCartney took out her third national title, but needed three attempts to clear her 4.55m opening height in the pole vault and could not challenge 4.70m.
"It wasn't great," she admitted. "The conditions were really nice and it was a great crowd, but I just wasn't feeling it today - it happens every now and then.
"I had 11 hours' sleep, I wonder if I slept for too long."
Walsh was similarly unpushed for his eighth national shot crown, perhaps suffering from the absence of fellow Olympic finalist Jacko Gill, who withdrew last week with injury.
Still, he produced a consistent series that culminated in a best of 21.51m, still world class, but not what he had hoped for.
"I was starting to get some really big throws in training and getting things moving a lot better, and I thought if I tagged one today, I would have gone pretty well.
"But I wasn't throwing through the shot, I was just turning around at the front and not lining them up.
"For a bad day, it wasn't too bad either. If I can beat 21 metres four times without actually hitting one, that's still a step in the right direction."
Further down the senior shot order, Jack Lewer of Manawatu added more than a metre to his Paralympic F20 record with 10.47m.
Back on the track, Olympian 800m representative Angie Petty showed her strength, returning to just 24 hours after winning her specialist event to retain her 1500m title.
Petty had run herself into the ground, outsprinting rival Katherine Camp in the shorter distance, and was content to sit and kick on Camille Buscomb over the longer journey, recording 4m 19.54s.
NZ Track & Field Championships
Porritt Stadium, Hamilton
Sunday, March 19
Men
200m: Joseph Millar (Waikato BOP) 20.37s 1, Will Smart (Auckland) 21.64s 2, Zac Topping (Manawatu Wanganui) 21.93s 3.
1500m: Eric Spearman (Hawkes Bay Gisborne) 3m 49.90s 1, Samuel Bremer (Otago) 3m 51.44s 2, Peter Wheeler (Auckland) 3m 52.57s 3.
400m hurdles: Cameron French (Waikato BOP) 51.58s 1, Campbell Wu (Auckland) 54.81s 2.
3000m steeplechase: Jack Beaumont (Southland) 9m 13.58s 1, Harry Burnard (Wellington) 9m 50.62s 2, Mathew Rogers (Lower Hutt) 10m 12.93s 1.
20km walk: Graeme Jones 1h 41m 42s 1.
4x400m: Manawatu Wanganui 3m 19.33s 1, Waikato BOP 3m 19.91s 2, Canterbury 3m 20.25s 3.
Javelin: Ben Langton-Burnell (Manawatu Wanganui) 76.59m 1, Stuart Farquhar (Waikato BOP) 71.23m 2, Alex Wood (Waikato BOP) 68.86m 3.
Shot: Tom Walsh (Canterbury) 21.51m 1, Ryan Ballantyne (Waikato BOP) 16.66m 2, Alexander Parkinson (Auckland) 15.20m 3.
High Jump: Hamish Kerr (Manwatu Wanganui) 2.15m 1, William Crayford (Wellington) 1.97m 2, Liam Speer (Auckland) 1.97m 3.
Triple Jump: Ebuka Okpala (Auckland) 15.43m 1, Scott Thomson (Wellington) 14.54m 2, David Van Den Bogaard (Auckland) 13.91m 3.
Pole Vault: Nick Southgate (Auckland) 5.15m 1, Vincent Hobbie (Germany) 4.85m 2, James Steyn (Auckland) 4.65m 3.
Men U20
200m: Bailey Cotton (Tasman) 22.25s 1, Nick Smith (Wellington) 22.45s 2, Jarvis Hansen (Canterbury) 22.47s 3.
1500m: Theo Quax (Auckland) 4m 11.72s 1, Oli Chignell (Otago) 4m 12.25s 2, James Uhlenberg (Auckland) 4m12.51 3.
400m hurdles: Oliver Miller (Auckland) 55.92s 1, Isaac Milne (Waikato BOP) 58.13s 2, Maselino Fua Valaoga (Samoa) 59.43s 3.
4x400m: Otago 3m 23.41s 1, Auckland 3m 29.63s 2, Waikato BOP 3m 30.86s 3.
3000m steeplechase: Blair Pennell (Waikato BOP) 10m 30.95s 1.
10km walk: Michael McElwee (Auckland) 1h 06m 46s 1.
Triple Jump: Christopher Goodwin (Waikato BOP) 14.27m 1, Matt Walsh (Canterbury) 13.99m 2, Andrew Allan (Southland) 13.12m 3.
Men U18
200m: James Guthrie-Croft (Auckland) 21.98s 1, Dominic Overend (Auckland) 22.23s 2, George Kozlov (Auckland) 22.71s 3.
1500m: Nick Moulai (Canterbury) 3m 52.95s 1, Isaiah Priddey (Waikato BOP) 3m 53.93s 2, Sam Hyde-Smith (Wellington) 3m 58.35s 3.
300m hurdles: Olly Parkinson (Auckland) 37.97s 1, Joshua Shih (Auckland) 39.64s 2, Louis Andrews (Canterbury) 40.25s 3.
2000m steeplechase: William Sinclair (Waikato BOP) 6m 10.05s 1, Murdoch McIntyre (Auckland) 6m 10.16s 2, Mark Day (Hawkes Bay Gisborne) 6m 25.10s 3.
Shot Put: Nick Palmer (Hawkes Bay Gisborne) 19.20m 1, Hamish Mears (Otago) 14.95m 2, Nikolas Kini (Northland) 13.24m 3.
Javelin: William Sinclair (Waikato BOP) 6m 10.05s 1, Murdoch McIntyre (Auckland) 6m 10.16s 2, Mark Day (Hawkes Bay Gisborne) 6m 25.10s 3.
Paralympic Men
200m: Lachlan Foote (International) 25.43s 1, Ethan Rangi (Auckland) 25.56s 2, Keegan Pitcher (Auckland) 25.84s 3.
1500m: Sunil Fernandez-Ritchie (Waikato BOP) 5m 05.31s 1, Guy Harrison (Hawkes Bay Gisborne) 5m 42.07s 2.
Shot Put: Jack Lewer (Manawatu Wanganui) 11.52m 1, Ben Tuimaseve (Auckland) 10.02m 2, Aodhan Hamilton (Waikato BOP) 9.81m 3.
Women
400m hurdles: Anna Percy (Canterbury) 60.23s 1, Megan Kukichi (Auckland) 62.30s 2, Celine Pearn (Auckland) 62.90s 3.
3000m steeplechase: Rosa Flanagan (Canterbury) 10m 38.72s 1, Natalie Dryden (Canterbury) 11m 31.43s 2.
20km walk: Erin Talcott (International) 1h 39m 53s 1, Rozie Robinson (Canterbury) 1h 43m 23s 2, Laura Langley (Hawkes Bay Gisborne) 1h 48m 58s 3.
Triple Jump: Anna Thomson (Wellington) 12.34m 1, Atipa Mabonga (Southland) 12.02m 2, Dian Ismagilova (Auckland) 11.85m 3.
Pole Vault: Eliza McCartney (Auckland) 4.55m 1, Hannah Philpot (Auckland) 3.65m 2, Katrin Pfitzner (Auckland) 3.30m 3.
Women U20
1500m: Kelsey Forman (Wellington) 4m 39.35s 1, Harriet Bush (Canterbury) 4m 39.52s 2, Zia Macdermid (Manawatu Wanganui) 4m 41.34s 3.
400m hurdles: Amanda Fitisemanu (Tasman) 62.99s 1, Tegan Duffy (Canterbury) 64.81s 2, Ruby Hansen (Hawkes Bay Gisborne) 64.95s 3.
3000m steeplechase: Amanda Holyer (Auckland) 11m 53.94s 1, Hannah Haworth (Waikato BOP) 12m 42.50s 2, Sami Jordan (Tasman) 12m 46.25s 3.
4x400m: Hawkes Bay Gisborne 3m 57.80s 1, Tasman 3m 59.04s 2, Waikato BOP 4m 00.22s 3.
High Jump: Alexandra Hyland (Auckland) 1.69m 1, Adriana Mawhinney (Otago) 1.65m 2, Imogen Skelton (Wellington) 1.60m 3.
Women U18
200m: Maia Broughton (Canterbury) 24.75s 1, Leah Belfield (Waikato BOP) 24.97s 2, Letisha Pukaikia (TaranakI 25.85s 3.
1500m: Hannah O'Connor (Taranaki) 4m 30.35s 1, Lily Trotter (Canterbury) 4m 35.15s 2, Phoebe McKnight (Wellington) 4m 38.50s 3.
300m hurdles: Olivia Burham (Canterbury) 44.59s 1, Zoe Taylor (Auckland) 44.89s 2, Alessandra Macdonald (Waikato BOP) 46.07s 3.
2000m steeplechase: Charli Miller (Waikato BOP) 6m 46.74s 1, Tessa Webb (Manawatu Wanganui) 6m 59.34s 2, Liliana Braun (Canterbury) 7m 10.54s 3.
Hammer: Mallata Tatola (Auckland) 56.17m 1, Savannah Scheen (Auckland) 45.26m 2, Alana Ryan (Taranaki) 44.90 3.
Paralympic Women
200m: Anna Grimaldi (Otago) 26.34s 1, Libby Leikis (Wellington) 35.12s 2, Anna Steven (North Harbour Bays) 35.33s 3.
