She didn't dwell on herself for long; being deputy to Andrew Little, the aim was to complement him, not to overshadow him.
The backbone of her speech was a major election promise – that every state secondary school would get a health professional as part of a comprehensive school-based health service to address mental health.
Her broader mission was to drag the youth vote to Labour from its apathy, alienation or allegiance to the Greens.
But she presented such a convincing figure of her own teenage years that she seemed a bit like a teen herself at that conference.
The extraordinary turn of events since then means that until this weekend, Ardern had not addressed a Labour conference as party leader.
She has undertaken many major speeches as Prime Minister in the past year, including most recently a substantial one to the United Nations General Assembly, but not as leader or Prime Minister to a Labour Party conference.
Last night's brief welcome to delegates in Dunedin will have been the first, ahead of her keynote speech to conference tomorrow.Ardern's transition from self-conscious deputy last conference to accomplished Prime Minister today will be clear.
It is a safe assumption that this will be one of the most genuinely buoyant conferences Labour has had since 2000 – which was the first conference after the Fifth Labour Government was elected under Helen Clark's leadership.
The message behind closed doors – and a huge amount of the conference is closed - will be to caution delegates against arrogance and to maintain discipline.
It is only the third time a Labour annual conference has been held in Dunedin: the first in 1948 shortly after World War II, in 1988 when the party was in the throes of a civil war over Rogernomics, and now in the relative tranquillity of 2018.
It is certainly the first decent chance Labour has had to stamp its colours on the Ardern Government since it was formed a year ago. Until now, brand-Labour has been somewhat subsumed by brand-Jacinda.
That hasn't been a bad thing given the value of her brand and the fact the party's most visible contribution to the Government was the hopelessly handled summer camp assault complaints, which are still before the courts.
The failure of judgments was a low point for the party and for Ardern too, along with her handling of the Derek Handley saga.
The other reason Labour is not heavily branded with the Government is New Zealand First's insistence that the term "Labour-led Government" be banished from political parlance.
Shane Jones this week referred to the "Jacinda Ardern Winston Peters-led Government."
When power sharing is the goal of the junior partner, there is less room for the bigger party, although that is an indulgence that cannot persist to the same extent in election year.
The party itself may not be heavily branded within the Government at present but there is no shortage of landmark Labour policies.
Labour's new generation leadership is less wedded to the incrementalism of the Clark-Cullen years in which much attention was given to the avoidance of alienating middle-New Zealand.
The configuration of the current Government has changed that dynamic. Labour has to accommodate the policies of two large and demanding parties in the Greens and New Zealand First – much larger than partners of National were.
But that also means there is no point in Labour incrementalism while other parties have got their wish lists. Labour has been equally ambitious with its own big ticket items such as fees free, the families package and KiwiBuild.
Any fear of alienating middle New Zealand must have diminished for Labour since the experience of last election when it was clearly the personality of the leader and not a change in policy that changed everything.
The exception to that is capital gains tax which tripped up Ardern in the election campaign and forced her to retreat on timing, from this term to next term.
Formulating a sellable capital gains tax after the working group report in February will be the biggest challenge to the sense of nirvana in which Labour finds itself.
There is little chance Ardern will drop it altogether. She is nothing if not bold.
Her move to make herself Child Poverty Reduction is the boldest allocation of any Prime Minister in recent times. It is a portfolio that will be judged on empirical results, not photo ops.
She has also been bolder on social issues than previous Governments. No one has had the courage to take on the abortion issue and cannabis use to the same extent.
National's high ratings this year have shown Labour the value of having a strong brand to sustain them long after high-profile leaders depart.
National has also prosecuted Labour successfully over petrol prices and law and order issues including the case of Karel Sroubek.
But there is now a spring in the step of Labour insiders whose polling suggests National is taking a much bigger hit from the disarray created by Jami-Lee Ross than the Colmar Brunton poll indicates.
National's internal woes coincide with a period in which Ardern is improving by the month.
This weekend is likely to show she is becoming a leader of substance.