|2015 Beijing||5000 m|
|World Indoor Championships|
|2014 Sopot||3000 m|
|2011 Maputo||1500 m|
|2012 Porto Novo||1500 m|
|2014 Marrakech||5000 m|
|2014 Glasgow||5000 m|
|2014 Marrakech||3000 m|
Born in Machakos, he was the son of a javelin thrower, David Ndiku, but he decided not to follow his father and focused on running instead. He began his career in domestic cross country running competitions and at the Athletics Kenya series meeting in Meru, he took fifth place in the junior men's race at the age of sixteen. He won selection for the 2009 World Youth Championships in Athletics with a personal best run in the 1500 metres at the Kenyan youth trials. At the championships in Brixen, he ran 3:38.42 to win the silver medal behind compatriot Gideon Kiage Mageka. Ndiku returned to the Kenyan cross country circuit at the end of the year, and finished fourth at another Athletics Kenya series race in Nairobi.
Ndiku earned himself a place on the Kenyan junior men's team for the 2010 IAAF World Cross Country Championships with a third-place finish in the junior race at the Kenya National Cross Country Championships. In the world junior men's race in Bydgoszcz the following month, he formed part of the leading pack before quickening the pace to establish a significant lead. He won the junior title and also headed the Kenyan runners to the team gold as the country grabbed the top four spots. Ndiku took his second title of the year at the 2010 World Junior Championships in Athletics, where he ran a personal best of 3:37.30 minutes to win the 1500 m world junior crown. He won the Most Promising Kenyan Sportsman of the Year award at the end that December.
In 2011 he started his technical collaboration with the Italian coach Renato Canova, who planned for him a strategy looking at 5000m.
In 2014 he had a very impressive season, winning everything possible : World Indoor Championships in 3000m, Commonwealth Games (27 July) in 5000m, African Championships (14 August) in 5000m, the Diamond League in 5000m (with two victories in Eugene and Zurich), and the Continental Cup in 3000m (14 September), becoming the number one of 5000m for the ranking of Track and Field.
|2009||World Youth Championships||Brixen, Italy||2nd||1500 m||3:38.42|
|2010||World Cross Country Championships||Bydgoszcz, Poland||1st||Junior race||Individual|
|World Junior Championships||Moncton, Canada||1st||1500 m||3:37.30|
|2011||All-Africa Games||Maputo, Mozambique||1st||1500 m||3:39.12|
|2012||African Championships||Porto Novo, Benin||1st||1500 m||3:35.71|
|2014||World Indoor Championships||Sopot, Poland||1st||3000 m||7:54.94|
|Commonwealth Games||Glasgow, Scotland||1st||5000 m||13:12.07|
|African Championships||Marrakech, Morocco||1st||5000 m||13:34.27|
|Continental Cup||Marrakech, Morocco||1st||3000 m||7:52.641|
|2015||World Championships||Beijing, China||2nd||5000 m||13:51.75|
|2016||World Indoor Championships||Portland, United States||5th||3000 m||7:58.81|
|Olympic Games||Rio de Janeiro, Brazil||18th (h)||5000 m||13:26.63|
- Butler, Mark (2010-03-28). Front running pays off for Ndiku – Men's Junior race report – Bydgoszcz 2010. IAAF. Retrieved on 2010-03-31.
- Makori, Elias (2008-11-29). Korikwiang collects second series win, Chebon sprints to men’s title – AK XC Meet 3. IAAF. Retrieved on 2010-03-31.
- Macharia, David (2009-06-16). Kenya selects its team for Bressanone. IAAF. Retrieved on 2010-03-31.
- Ndiku Caleb Mwangangi. IAAF. Retrieved on 2010-03-31.
- Martin, David (2009-07-12). Williams and James achieve unprecedented doubles as Kenya steals the show in middle distance – Day Five – Evening report. IAAF. Retrieved on 2010-03-31.
- Njenga, Peter (2009-11-29). Cherono dominates – AK 3rd weekend XC fixture. IAAF. Retrieved on 2010-03-31.
- Makori, Elias (2010-02-20). Tanui emerges while Masai pounces as Kenya selects squad for Bydgoszcz. IAAF. Retrieved on 2010-03-31.
- Martin, David (2010-07-23). 2010 – Kenya's Ndiku thwarts rivals with gun-to-tape 1500 win – Day Four Evening Wrap. IAAF. Retrieved on 2011-03-29.
- The Standard, December 11, 2010: Rudisha and Lagat crowned Soya best athletes
- Sampaolo, Diego (2011-03-28). Another cross country win for World champion Merga – Alà dei Sardi report. IAAF. Retrieved on 2011-03-29.