Complexity can embrace Holism but it is not restricted to Holism.
Holism is interesting as a theory against the Reductionism, but sometimes Holism has its "traps".
Holism can be a kind of Reductionism if it only accept the "vision of the whole" has the unique approach to Reality... So it can become another "reductionist tendency", if it reduces everything to "the whole".
Holism appeared in Modern times but it became a strong and maybe "fashioned" way of thinking in Postmodern Era, because it was a strong way to oppose to Reductionism.
The Postmodern Era was a time of "strong polarity" with Reductionism at one side and Holism at the other.
In the After-Postmodern times, Complexity can embrace traces of reductionistic and holistic tendencies but going beyond polarities.
Systems Theory is also interesting and can also be embraced by Complexity. But, as Edgar Morin wrote in his great work "La Méthode", Systems Theory can have also a kind of "trap" that we could say can be similar to Holism.
So, Holism and Systems Theory are good tools to better understand Reality, but Complexity can help us to do not reduce Reality to any of both ways of thought.
The third pillar of Transdisciplinarity, "the third included" can harmonize paradoxes. It can help to harmonize reductionistic and holistic tendencies.