The charity wants to increase the number of children it helps directly by 25% to 10,000 annually and offer support to a further 20,000.
Believe in Me launches on Thursday and will also tackle a perceived lack of confidence in 11 to 18-year-olds.
The move comes on the back of a UK-wide survey that found most youngsters in the age bracket lack confidence.
In total, 2,000 youngsters were questioned, with 88% saying they were low in confidence - 96% of the 200 young people questioned in Wales gave that answer.
To address this, the charity wants to increase the Â£2.37m it raises annually in Wales to help youngsters dealing with things like poverty, homelessness, disability and bereavement to help reach more people.
Barnardo's Cymru director Sarah Crawley called the confidence study results "a wake up call".
She said: "We will be galvanising our work around three strategic aims: stronger families, safer childhoods and positive futures.
"Through these aims we will not only be meeting the needs of children and young people now, but looking into the future to prevent them from occurring."
About 30,000 vulnerable children will be helped each year, in plans to be announced by Barnardo's Cymru.